Place lamb in large non-aluminum roasting pan. Rub with garlic. Season with salt and pepper. Combine remaining ingredients in small saucepan. Simmer until onion is soft, stirring occasionally, about 10 minutes. Remove from heat; cool. Pour over lamb. Cover and refrigerate overnight, turning occasionally. Prepare barbecue (medium-high heat) or preheat broiler. Remove lamb from marinade and cook fat side up 10 minutes. Turn and cook until brown around edges and pink in center, 10 to 15 minutes. Serve immediately. lamb 25