Trim fat from ribs. Place in shallow baking pan; sprinkle with lemon and onion. Add 1/2 cup water. Bake, covered with foil, at 350F for 1 hour. Combine remaining ingredients in saucepan. Simmer for 10 minutes or until slightly thickened. Remove spareribs to work surface and drain pan well. Cut ribs into serving pieces. Return to baking pan; brush with 1/3 of the sauce. Bake, uncovered, for 45 minutes or until tender, brushing frequently with sauce.