Preheat oven to 450°F.
Place pork spareribs in a shallow roasting pan, meat side up. Place a slice of unpeeled lemon and a thin slice of onion on each rib. Roast for 30 minutes.
Meanwhile, in a saucepan, combine ketchup, Worcestershire sauce, chili powder, salt, hot pepper sauce and water. Bring to a boil, then pour over the ribs at the end of the first 30 minutes. Lower heat to 350°F and continue baking for about 2 hours, basting the ribs with the sauce every 15 minutes.