How to Make It
Heat oven to 450° F. Halve 1 lemon and rub it all over the lamb. Squeeze its juice into a small bowl; mix with the garlic and rosemary. Cut 10 slits, 1 to 2 inches deep, all over the meat. Stuff the cuts with the garlic mixture. Rub the meat with 1 tablespoon olive oil and season with 1 tablespoon salt.
Place the lamb in a roasting pan and roast for 30 minutes. Turn over and roast for 40 minutes more or until the thickest part of the meat registers 145° to 150° F. Remove from oven; let rest 10 minutes.
Menu plan: Cut off 1/4 of the lamb meat and reserve for White Bean and Lamb Chili.
Meanwhile, in a large bowl whisk together the mustard, juice from the remaining lemon, remaining oil, and salt. Fold in the beans, shallot, and parsley.
Menu plan: Reserve 2 cups of the beans for White Bean and Lamb Chili.
Thinly slice the remaining lamb and serve with the white beans and Lemon Spinach.