Are you looking for a new and delicious way to prepare beef tenderloin (the loin from which filet mignon is cut) on the grill? Would you be interested in something that might cause your friends to accidentally blurt out profanity both when they see the cooking method and when they taste how good it is? If so then you should consider grilling a “lomo al trapo.”
Lomo al trapo, is literally translated as “beef tenderloin in a towel”. And unless you are familiar with Colombian grilling, it is likely to be unlike anything you have made on the grill previously. Described in its simplest terms, it is beef tenderloin wrapped in salt and cloth and cooked directly on the coals.
Fortunately, it is easy to prepare and yields some of the most tender and tasty tenderloin that you are likely to have tried. It will also provide an interesting show for your guests.
One thing you will have to have is a charcoal grill or at least a fireplace. It is not uncommon for Colombians to grill lomo al trapo in the fireplace sometimes.
The other requirements are:
1 beef tenderloin – I usually like a medium sized one. It needs to be trimmed of fat and silver skin (your butcher will do this for you).
1 piece of clean cloth approximately 16 inches square – You can use old bed sheets, shirts,cotton dish towel, etc. Just make sure they are washed well to remove any starch, etc.
Plenty of coarse salt – You will need at least 2 cups of salt, enough to evenly coat the cloth with ¼ inch of salt. You can use fine grained salt if that is all you have, but it is a little more difficult to work with and yields saltier meat. You read that amount right. Don't worry, most of this will be brushed off before serving. The salt helps to protect the meat while it's on the flame.
Seasoning you may wish to add – It is great with just salt, but you can add herbs and other seasonings. Oregano is frequently added, but I have also seen garlic, cilantro and black peppercorns used as well.
Optional – red wine or water
Build your fire before you begin wrapping the loin. If you wrap it too early too much water will be drawn out of the meat. It will eventually draw some of the water and salt back into the meat, but given the amount of salt used this can be tricky to gauge and control. So start by building your fire and letting your coals nice an hot. We use a Big Green Egg for our lomo, but you can use any charcoal grill, a camp fire, fireplace, etc. Just don't try this on a gas grill. Also we use lump charcoal. However, I have seen instructions that say you can also get good results with briquettes.
Once your fire is ready its time to wrap the loin. Some prefer to soak the cloth in red wine or cold water to start. This can help prevent the cloth from burning too fast during the cook, but it is not necessary. The vast majority of times I grill lomo al trapo without soaking the cloth in anything. If you do soak the cloth, wring it out fairly well before covering with salt.
Lay out the cloth on a flat surface. Cover the surface of the cloth with ¼ to ½ inch of salt. Leave about an inch or two around the edges of the cloth without salt. Try to make the salt as level as possible, but there is no need to be too concerned about this.
Once the cloth is covered with salt, lay the tenderloin on one edge, parallel to the edge. If the cloth is not square, lay the meat on the long edge. Then begin rolling up the meat in the cloth. Try to make the roll reasonably tight, compact and even. This will help the lomo cook relatively evenly.
When finished rolling, Use the butcher's twine to tie the roll. Tie around the roll approximately every couple of inches. If the ends of the cloth are long enough, you can tie then together over the roll. If not, simply tie the ends off with the twine. Now you are ready to put the lomo at trapo on the fire.
Place the meat directly on the hot coals - not on the grate. This will be seem strange the first time you do it and will likely cause some concern among unintiated dinner guests. Their concern will only deepen as the cloth begins to blacken and char. Don't worry, however, soon their concerns will turn to amazement at the tender and flavorful meat that emerges.
The novice cook will likely be concerned as well. As it cooks, the roll will begin to look like a charred log. This is normal.
Cooking time will vary. There are a lot of instructions that say to cook the lomo 9 minutes on one side and 8 minutes on the other. I have found this to be a general guideline but by no means perfectly reliable. Start with 9 minutes on one side and 8 on the other then check the tenderloin with a thermometer (we have reviewed several here). Frequently my lomos have needed more time.
We like ours medium rare. So we usually cook the meat to around 120 degrees before taking it out of the coals. Many like tenderloin on the rare side, so they will cook until 95 degrees Fahrenheit then let the meat sit while it continues to cook. The salt crust will hold a lot of heat. So considerable cooking will continue if the meat is left to sit in the roll after being taken off of the fire.
There can be a minor hiccup in a cook. This usually involves a part of the towel/salt covering burning too much or a part cracking off. If this happens you can place the covering back on the meat as much as possible and cover the roll in tinfoil (wearing protective gloves of course). Sometimes you might also remove the meat too early and find that it does not cook long enough to reach the desired or safe temperature. Again you can wrap the meat in tinfoil and place in the oven cook to the desired temperature.
You can see in the image above that part of the meat was exposed during the cook. The meat was still delicious - it was not affected in the least.
Once you are ready to serve the meat, remove it from the salt and towel shell. Sometimes you may need to crack the shell with the back of a heavy knife. When the meat is out of the shell brush off the outer crust of salt with a brush or towel. Finally slice in pieces an inch or so thick and listen to the expressions of amazement from your family and guests.