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Lomo al Trapo: The Colombian Technique That Will Change the Way You Grill Beef

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This is absolutely the most showstopping way to present beef tenderloin. [Photographs: J. Kenji López-Alt]

Remember that scene at the end of Ghostbusters when the boys in gray crack Sigourney Weaver out of the petrified remains of the ghost dog Zuul? Picture that scene at your next dinner party, but instead of a whip-smart and attractive actress emerging from the carbonized crust, it’s a perfectly cooked hunk of beef tenderloin. That’s what we’re gonna make happen today, and I promise it’s a heck of a lot better than barbecued dog hair.

My wife is Colombian, and at this point I’ve been to the country often enough that I’ve gotten accustomed to its eating culture, aware of its most classic dishes and regional specialties. So I was pleasantly surprised when, on my most recent visit, her family suggested we try lomo al trapo, a preparation I’d never heard of.* Literally translated as “beef tenderloin in a towel,” it’s made by wrapping a big chunk of beef tenderloin in a thick crust of salt swaddled in a towel, tying it up, and throwing it directly on a fire until it’s cooked.

It’s one of the easiest, most foolproof, primally delicious, and downrightimpressive methods of cooking beef I’ve ever seen. I flat-out guarantee that every single one of your guests will be floored. All it takes is three ingredients, a few basic kitchen supplies, and a fire. No pots, pans, or even a grill required.

On a chilly Sunday afternoon in Bogotá, when there’s already a fire going in the fireplace, it’s not an uncommon practice to throw a towel-wrapped hunk of beef into the coals in time for dinner. My wife, Adri, says her family used to do it as a special treat at her aunt and late uncle’s home in Subachoque.

My mother-in-law’s mother once built a house, which, at the time, was located in a deep suburb of Bogotá, but is now just another part of the sprawling cityscape (think: the old guy’s house from Up). After her death, it was left to her three daughters—my mother-in-law and her two sisters—who, in an odd twist of events, have been leasing it for nearly three decades to a restaurant that specializes in lomo al trapo. The chef was kind enough to let me walk into the kitchen to observe him in action as he prepared their signature dish.

He started by trimming a large, center-cut piece of beef tenderloin. Tenderloin is always a lean cut, but the tenderloin in Colombia is especially so, though Colombian beef makes up for its leanness with a very hearty, almost gamy flavor. He then showered a clean, damp towel with a ton of salt—covering a rectangle about 10 inches wide and 12 inches long with a depth of about half an inch—and placed the beef on top of it. He quickly rolled the beef up in the cloth, folding in the sides like a burrito to create a tight parcel, which he wrapped with cotton twine and tossed directly onto a bed of glowing coals.

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“That’s it, I’m finished,” he said to me, adding that the only thing he had left to do was flip it in 10 minutes. I looked at the bed of coals to see three or four more of the parcels at various stages of cooking—some engulfed in flame as the outer layers of cloth burned away, others more closely resembling carbonized tree stumps after a forest fire.

About 15 minutes later, a server carted our finished lomo al trapo tableside and presented it to us on a large steel platter. He then cracked the crust with the back of his knife. Over the course of its cooking time, the salt ended up drying and solidifying into a brittle crust, the cloth nearly disintegrating. The beef came out of its shell with considerable ease, and the server used the back of his knife to clean it of excess salt before transferring it to a fresh platter.

Next, he poured a cup of brandy over the lomo and ignited it with an extravagant and completely nontraditional flourish, letting the outside of the meat singe and color a bit before the flames died out naturally. Finally, he started slicing and serving the beef to us (Russian table service! I haven’t seen that in ages) with a choice of Argentinean chimichurri or a Colombian ají (chili sauce).

The beef was incredibly tender and had a definite strong gradient, the center a very deep red and the edges more well-done. This isn’t a roast for people who really value the perfectly edge-to-edge pink look, but it’s hard to argue with a piece of beef when even its well-done sections are flavorful and moist. Considering that it’s literally cooked in salt, the meat is surprisingly unsalty—most of the saltiness is concentrated, predictably, around the edges. It comes out with a hint of smokiness from the burnt cloth and a crust that’s a little hard to describe. It’s nothing like the crackly brown crust of a naked grilled steak, but it’s definitely got some texture and richer flavors going on, and, of course (at least in this case), a hint of brandy. Certainly the awesomeness of the presentation enhances the flavor of the beef as you eat.

There was no doubt in my mind: This dish was destined to become my big backyard party trick for the foreseeable future. I just needed to iron out some wrinkles in that cloth.

* In retrospect, I probably should have heard of this dish before, seeing as Kristen Miglore wrote about Steven Raichlen’s version of it for her Genius Recipes column over on Food52 a few years ago, but somehow that post had managed to slip by me. Not only that, but Adri claims that her family has been making it for ages.

SALTY SUSPICIONS

Thus far, every recipe I’d seen—including the one used at the restaurant in Bogotá—called for using fine granulated salt as opposed to flaky kosher salt or large-crystal sea salt. But is it really the best salt to use? I cooked three chunks of tenderloin side by side to find out.

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From a construction standpoint, I found that kosher salt and large-crystal sea salt (I used Maldon) were easier than fine-grained salt, which had a tendency to flow out of the ends of the cloth package and was small enough to slip through gaps in cheesecloth when I used cheesecloth in place of a towel.

Performance-wise, they all came out about the same. The beef chunks themselves were pretty indistinguishable, though the beef cooked with finer salt was also saltier in the end—it was difficult to brush off all the excess salt after cracking open the crust. The coarser salts had another advantage: After cracking off that crust of salt, you can crumble it with your fingertips and use the smoky salt to season the interior portions of the beef or your side dishes as you eat, adding another layer of complexity. Much easier to do with coarse grains than with fine.

In the end, I chose to go with kosher salt. It’s easier to work with than granulated table salt, and it’s far less expensive than a fancy finishing salt.

Next, I wondered about how much salt and how long to let the meat sit in its salt crust before cooking it. Turns out that the quantity doesn’t matter all that much so long as you hit a thickness of at least half an inch or so. Timing, however, does make a difference.

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Meat allowed to rest for eight hours in a salty crust before cooking loses a ton of its weight through osmosis, as its juices get pulled into the salt and eventually evaporate during cooking. Cut the crust open on a long-salted roast, and there’s a good half inch of space all around it that used to be occupied by meat. It also comes out inedibly salty. Make sure you cook the beef immediately after wrapping it.

TOWELS AND TIMING

I tried a couple of different types of material and various configurations for optimal rolling. I found that laying out a clean cotton dish towel, with the short edge parallel to your board, is the easiest way to work and forms the tightest salt seal. To me, this configuration is easier than the diagonal configuration I’ve seen in some other recipes. Dampening the towel with a little cold water also plays a small role in helping the salt crust stiffen up as it cooks, though it’s no big deal if you forget to dampen the towel—it’ll come out just fine.

I’ve seen it suggested that cheesecloth makes a good replacement for folks who don’t want to waste a towel. I’ve made the recipe with cheesecloth, and it works. But given that you need at least a quadruple layer of cheesecloth to form a mesh tight enough to hold the salt against the meat, a cheesecloth version actually winds up costing more than simply using an inexpensive cotton dish towel.

The ones I ordered off Amazon in a 15-pack are just over a buck per towel. Not bad.

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Traditional recipes use the embers of an actual wood fire for the cooking medium, though I found that a bed of charcoal briquettes also works just fine. Unfortunately, you can’t do it on a gas grill—it simply doesn’t get hot enough—but this might be a good trick to unveil on a camping trip. One night, I cooked a lomo al trapo along with a half dozen in-the-husk ears of corn, which I threw directly on the coals surrounding the beef. That’s a full camping dinner right there (and one of the best ways to grill corn, incidentally).

The final and most important key to the lomo al trapo puzzle is knowing how long to cook it. I found that, as usual, timing is a wildly inaccurate way to gauge doneness. There’s simply no way to account for variances in heat, thickness of meat, thickness of salt crust, air temp, wind, weather, or any of the dozens of other factors that affect outdoor cooking. Instead, I relied on my trustyThermapen thermometer.

Unlike fattier cuts, which I prefer in the medium-rare to medium range, I like my lean tenderloin solidly rare. Any more cooked, and it dries out. For the first several batches, to account for carryover cooking, I pulled it off the fire when it was 10 to 15 degrees below my final target temperature of 120°F, but I found time after time that it came out overcooked and dry. Then I realized my mistake: That thick salt crust hangs on to a ton of heat energy, so there’s significantly more carryover cooking in a lomo al trapo than in a naked tenderloin. Pulling the tenderloin off when the core reached 95°F, a full 25°F below final temperature, proved to be the solution. It can take anywhere from 10 to 20 minutes or so of resting to reach the target temp.

LOMO AL TRAPO, STEP BY STEP

You convinced yet? Have you squared away your weekend dinner plans? Good. Here’s how to do it—and get ready, because it’s faster and easier than you think.

PREPARE THE BEEF AND TOWEL

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Start with a center-cut beef tenderloin, also known as a Chateaubriand. It’s a roughly two-pound roast consisting of the cylindrical center portion of a tenderloin, with the tapered end and the bulging fat end removed. It’s large enough to feed four hungry or six normal people. I attempted making the dish with a full tenderloin by folding back the tapered end and doubling it onto itself to even out the shape, and it worked just fine (though I had to find a larger towel, and wrapping was far more cumbersome).

Assuming the butcher has already trimmed the tenderloin of silver skin and connective tissue, there’s nothing else you need to do with it. (If not, here’s our guide to trimming a tenderloin.)

Lay out that damp towel and cover it with a heavy layer of kosher salt—about a pound and a half to two pounds—spreading it close to the bottom edge of the towel and leaving a couple of inches of space on either side. Scatter whole herb sprigs, such as oregano, over the salt, then lay the tenderloin on top of the salt, aligned with the bottom edge.

START ROLLING

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Start rolling up the beef by picking up the leading edge of the towel and folding it over the beef. As you roll, keep things nice and tight so that the salt completely surrounds the beef. As the edge of the towel wraps over the beef and is about to get tucked inside the roll, pull it outward instead so that the beef is fully encased in salt before rolling that leading edge of the towel under it. Anyone who’s rolled sushi in a bamboo sushi mat should know this action (see the top right photo in the composite above for a visual).

Next, fold in the sides of the package like you would a burrito, then continue rolling until everything is neat, tidy, and tucked.

To secure the beef, you can use a series of bits of string tied with simple granny knots, though if you use a butcher’s knot, things will be tighter and smoother. If you know the technique, you can also tie it up with a single string for ultimate compactness, the way I did here—but honestly, so long as it holds together firmly, you’re good to go. This technique is pretty darn bulletproof.

LIGHT A FIRE AND GET COOKING!

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Using a charcoal chimney filled to the brim with coals (five to six quarts of coals), get a good, raging hot fire going in your grill, then spread the coals out over half of the cooking grate. Place the package directly onto the coals, nestling it in a little bit. You’ll probably see it immediately catch fire and start to produce red flames. This is okay, but if the fire threatens to completely burn away the strings or cloth, clamp a lid down on the grill and keep it slightly ajar to limit oxygen flow a little bit.

Once the first side has cooked for about 10 minutes, flip the whole package over with a set of long tongs. It will look like it’s burnt to all hell. This is fine and normal.

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Keep calm and carry on cooking.

WHAT IF IT BREAKS?

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There’s a chance that over the course of your cook time, you might accidentally manhandle the thing a little too much and prematurely crack the crust. This happened to me only once out of more than a dozen cooking sessions. Don’t worry. Just place the broken pieces back over the main chunk as well as you can and let it keep cooking. A little ash may end up on the surface of your meat, but you can always wipe it away later on.

TAKE THE TEMP

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To gauge doneness, use your instant-read thermometer to take the temperature of the beef once you hit the 15-minute mark. You can poke it straight through the cloth and salt crust; it should slide in with no real difficulty. You’ll want to poke around a bit to find the coolest spot. Once it hits 95°F for rare or 105°F for medium-rare, you’re done. Do not overcook tenderloin—it is the least forgiving of beef cuts.

I’d strongly advise against using a leave-in probe thermometer here. You’re cooking very close to the coals, and those leads are not designed to work with the extreme heat of a live fire. Stick with an instant-read.

As soon as the beef is done, transfer it to a metal tray and let it rest until the core hits 120°F for rare or 130°F for medium-rare, about 10 to 20 minutes.

CRACK AND SERVE

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Ready to serve? Good. It’s time for the big reveal to see if your careful tying and probing all worked out. Use the blunt back side of the knife to crack that salt crust in several places. It should crack open quite easily. Pull off all the large chunks and set them aside, then use the back of your knife to brush and knock away any excess salt that has stuck to the meat. Don’t worry—that crust is plenty salty, even without any visible grains.

If you really want to do the flambéing trick, return the meat to a heatproof pan or skillet, douse it with brandy, and carefully light it on fire, turning it every so often until the flames die out. It’s more about show than flavor, but damn, is it a pretty show.

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I like to do all this right in front of the guests before carving the beef into slices. Those spent bits of crust and the salt that’s flaked off the beef? Don’t discard it! It has a wonderfully smoky flavor and is the perfect condiment for the interior, unseasoned expanses of the beef, as well as whatever side dishes you’re going to be serving (like that buttered corn, or little boiled potatoes).

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The beef is plenty juicy and flavorful on its own, but if you want, an appropriate sauce would be either ají or Argentinean chimichurri. Either way, it’s a good bet your guests are going to be too impressed with the beef to care much about anything that’s going on around it.

Quick, while they’re distracted! Now’s your chance to sneak the last beer from the cooler, kick it back, and start pondering all the other things that might be cooked with this technique. Perhaps our chicken, pork chops, fish, and vegetables may never be the same, either…

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  • apopso

    I honestly think the meat looks terrible.