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.
Let stand at room temperature for 30 minutes. Preheat oven to 425 degrees F. Roast lamb in middle of oven for 20 minutes, reduce heat to 350, and cook until an instant-read thermometer inserted 2 inches into thickest part of meat (not touching bone) registers 135 degrees F, about 1 3/4 hours.et stand at room temperature for 30 minutes. Preheat oven to 425 degrees F. Roast lamb in middle of oven for 20 minutes, reduce heat to 350, and cook until an instant-read thermometer inserted 2 inches into thickest part of meat (not touching bone) registers 135 degrees F, about 1 3/4 hours.