In a small bowl, combine the garlic, lemon zest and juice, garum, and olive oil.

Place the lamb on a baking rack set over a roasting pan. Brush both sides of the lamb with the marinade. Place the lamb in the fridge uncovered for at least 1 day and as long as 2 days. I recommend to keep the marinating lamb in a cold mudroom or breezeway, as it’s important to leave it uncovered and the garlic will permeate other foods in your fridge if kept there.

If you’re feeling brave enough to cook outside, start a hot fire in a grill, or turn your broiler to high and place the rack as close to the heat as possible. Sear the lamb fat side down directly over the coals, or with the fat side up under the broiler.

Cook until well charred and flip to sear the meaty side. Cook until a thermometer reads 126°F in the thickest part of the meat. Remove from heat and rest 10 minutes before slicing as thinly as possible.