Grilled Butterflied Leg of Lamb

Ingredients

• 1/2 onion
• 4 cloves garlic, peeled
• 2 tablespoons fresh rosemary leaves, or 1 tablespoon dried
• Zest of 1 lemon
• 1 tablespoon apple cider vinegar
• 2 tablespoons extra virgin olive oil
• Kosher salt and freshly ground black pepper
• 1 boneless leg of lamb, 5 to 6 pounds, butterflied

Directions

1. Make the marinade by adding the onion, garlic, rosemary, lemon zest, apple cider vinegar, and olive oil to a food processor, then pulsing until combined. If you do not have a food processor, finely chop the onion, garlic, and rosemary, then stir them together with the remaining marinade ingredients.
2. Season the lamb generously with salt and pepper. Put the lamb and the marinade in a 1-gallon freezer bag, then work the marinade around so it coats the meat on every side. Close the bag and chill it for 1 to 2 hours. Take the lamb out of the refrigerator and let it sit until it loses its chill, about 20 minutes. When you are ready to grill, take it out of the marinade bag.
3. For easier flipping, slide a couple of skewers crosswise through the lamb.
4. Set up the grill. For a charcoal grill, arrange the coals with a double layer on one side and a thin single layer on the other side, so you have both hotter and cooler zones. For a gas grill, start by heating all burners on high; after the lamb is browned, you will turn the heat down.
5. Put the lamb on the hotter part of the grill, fat side facing down. Flareups are likely, so have a squirt bottle of water or a couple of cups of water nearby if you are cooking over charcoal and need to calm the flames. Sear the first side for 4 minutes, then turn the lamb and brown the second side for another 4 minutes.
6. Shift the lamb to the cooler area of a charcoal grill, or turn a gas grill down to low. Aim to hold the grill between 300-350 degrees F. Cover and continue cooking for 35-45 minutes, depending on the roast’s thickness and weight, until a thermometer in the thickest part reads 120 degrees F for rare or 130 degrees F for medium rare.
7. Move the lamb to a cutting board with a groove to catch the juices. Tent it with aluminum foil and rest it for 5-10 minutes. If you used skewers, pull them out.
8. Slice the lamb against the grain into 1/4 to 1/2-inch thick pieces. Arrange the slices on a warm platter, spoon the collected juices over the top, and serve with mint jelly or horseradish.