Place ribs in shallow roasting pan, meaty side up. On each piece, place a slice of un-peeled lemon, a thin slice of onion. Roast in very hot oven, 450 F degrees, 30 minutes. Combine remaining ingredients; bring to a boil and pour over ribs. Continue baking in a moderate oven, 350 F degrees, about 2 hours, basting ribs with the sauce every 15 minutes.