Directions. 1  Preheat oven to 450 degrees. 2  Season lamb racks with salt and pepper; coat each evenly with 3 Tbsp pesto. 3  Roast on baking sheet until about 5 degrees less than desired doneness (about 20 min for medium). 4  Transfer lamb to clean platter; let rest 10 min before slicing.
Preheat the oven to 400 degrees F. Using your hands, rub the lamb all over with the lemon juice. Pat the garlic and rosemary evenly all over the surface of the meat. Season the meat with the salt and pepper and place the lamb in a roasting pan. Place the lamb in the oven and roast for 30 minutes.
3. When ready to cook, place lamb on a wire rack set in a foil-lined rimmed baking sheet. Transfer to oven and roast until an instant read thermometer inserted into coolest section of lamb registers 125Â° to 130Â°F for medium-rare, or 130Â° to 135Â°F for medium, 3 to 3 1/2 hours.Remove from oven and let rest for 40 minutes.hile lamb is resting, increase oven temperature to 500Â°F. Return lamb to oven and roast until exterior is deep brown and crisp, about 15 minutes. Remove from oven and let rest 5 minutes. Remove twine with kitchen shears, transfer lamb to cutting board, slice into 1/4 inch slices, and serve.