1. Preheat the oven to 400°F.
2. Cut the rosemary into 1-inch pieces. Season the lamb with salt (in moderation) and pepper. Using a sharp knife, make small, 1-inch cuts in the meat and insert pieces of rosemary. Drizzle the meat with oil and 1 tablespoon vinegar.
3. Place in a baking dish and roast for 30 minutes, basting the lamb every 8-10 minutes with 1 tablespoon vinegar. Remove when an instant read thermometer inserted in the thickest part of the meat reads 145°F for medium rare. Let rest, loosely covered with foil, 10 minutes.
Per serving: 680 calories, 62g fat, 26g saturated fat, 129mg cholesterol, 99mg sodium, 3g carbohydrate, 1g fiber, 2g sugar, 25g protein