Coarse or kosher salt and freshly ground pepper to taste
Finely grated zest from 2 lemons
Rub the garlic and lemon zest all over the lamb, and season well with salt and pepper. Place in a bowl or on a plate and refrigerate overnight, uncovered.
Preheat the oven to 425°F. While the oven is preheating place the lamb on a rack in a roasting pan of some sort, and allow it to come to room temperature.
Roast the lamb for 20 minutes, then reduce the heat to 350°F and continue to cook for another 1 1/2 hours to 1 hour 45 minutes, until a meat thermometer registers 135° in the center of the meat. Start testing on the very early side. Remove from the oven and let it sit for 20 minutes to collect its juices and finish cooking before carving and serving.