Directions

1. Preparing the marinade: Place onion, garlic, rosemary, lemon zest, apple cider vinegar, and olive oil into your food processor and pulse to combine.
2. Season the lamb with a generous amount of salt and pepper, then put it into a 1-gallon freezer bag. Pour marinade over all sides of the meat, close the bag and refrigerate for 1 to 2 hours.
3. Remove lamb from refrigerator and place it on the counter for 20 minutes allowing it to come to room temperature.
4. Remove from marinade bag and stick a couple of skewers through the lamb, crosswise.
5. Preheating your grill: a. Charcoal Grill: Organize the coals so that they are double layered on one side of the grill, and sporadically single layered on the other side of the grill ("banked" grilling method). b. Gas Grill: Turn all burners on high to start. Reduce heat after the initial browning.
6. To sear the lamb, use the hot side of the grill (double layer charcoals side), put the lamb, fat side down. Typically, flare-ups will occur and you can control them with a squirt bottle of water or a couple of cups of water to control the flames. Sear one side for 4 minutes, flip the lamb over to sear the other side for another 4 minutes.
7. To finish cooking the lamb, move to cooler side of grill (for a gas grill, turn the heat to low). Cover the grill and cook for an additional 35 – 45 (this varies based on how thick and how many pounds the lamb is) minutes while maintaining a temperature of 300-350°F. Use a meat thermometer to check the temperature in the thickest part of the roast, it needs to be at 130°F (for medium rare).
8. Before cutting, let the roast rest covered in aluminum foil on a cutting board with a well to catch the juices for 5 – 10 minutes.
9. If you used skewers, remove them. Cut across the grain into 1/4 to 1/2-inch thick pieces and pour meat juices over the pieces.
10. 10. Serve with mint jelly or horseradish.