Place ribs in shallow roasting pan. On each piece, place slice of unpeeled lemon, thin slices of onion. Roast in hot oven for 30 minutes. Combine remaining ingredients and bring to a boil in small saucepan and pour over ribs. Continue baking in moderate oven for 1 hour. Baste ribs with sauce every 15 minutes. If sauce gets too thick, add more water.