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.
Place the lamb in a roasting or sheet pan with the ribs curving down, and coat the tops with the mustard mixture. Allow to stand for 1 hour at room temperature. Preheat the oven to 450 degrees F. Roast the lamb for exactly 20 minutes for rare or 25 minutes for medium-rare.Remove from the oven and cover with aluminum foil. Allow to sit for 15 minutes, then cut into individual ribs and serve.lace the lamb in a roasting or sheet pan with the ribs curving down, and coat the tops with the mustard mixture. Allow to stand for 1 hour at room temperature. Preheat the oven to 450 degrees F. Roast the lamb for exactly 20 minutes for rare or 25 minutes for medium-rare.