This classic spicy barbecue sauce has a mellow, rich flavor that is marvelous with just about anything you'd care to grill. Serve additional sauce on the side. ~- ~- In a heavy nonaluminum saucepan over medium heat, melt the butter and saute the onion, celery, pepper, and garlic for 5 minutes, or until the onion is tender but not browned. Add the remaining ingredients. Cover and simmer for 30 minutes, until the sauce thickens, stirring occasionally. Discard the lemon slices and bay leaf. Brush the sauce on chicken, ribs, frankfurters, or hamburgers during grilling, broiling, or baking. Makes 2-1/4 cup.