Step 1

Place the chopped lemon, rosemary, garlic, salt, pepper, and olive oil in a food processor. A blender can also be used, if done in batches. If you have neither, finely chop all ingredients together.

Step 2

Open up the lamb and lay it flat. Spread and massage the lemon paste evenly over the inside and outside of the lamb. Place in a baking dish and cover, or in a large resealable plastic bag. Refrigerate overnight to marinate, turning occasionally.

Step 3

Preheat the oven to 450 degrees. Remove the meat from the refrigerator 30 to 60 minutes before cooking. Place the lamb on a rack in a foil-lined roasting pan or rimmed baking sheet. Place the meat in the oven and after 5 minutes, reduce the temperature to 425 degrees. Roast for 45 minutes, or until medium rare, 140 degrees on an instant read thermometer. Allow the meat to rest for 10 to 15 minutes before carving and serving.