Tie garlic, bay leaves, allspice and cloves in double thickness of cheesecloth. Cut each slab of ribs in half. Put ribs and spice mixture into large Dutch oven; add cold water to cover. Heat to boil; reduce heat; cover, simmer 30 minutes, or until fork-tender. Drain.
Heat oil in large saucepan; add onion. Cook and stir until onion is tender. Stir in remaining ingredients. Simmer 20 minutes or until slightly thickened, stirring occasionally. Puree in food processor or blender.
Put ribs into shallow roasting pan. Generously brush ribs on both sides with sauce. Bake in a 350 degree oven about 30 minutes until sauce is bubbly and glazed, turning ribs occasionally and brushing with sauce.
For a more glazed look and a slightly crisper rib, broil 3 minutes, turning once.
Note: Four to five pounds of spareribs can be substituted for the back ribs. Simmer with spices for 45 minutes instead of 30 minutes. 4 servings.
