Preheat oven to 35° F.
Arrange ribs, slightly overlapping, in large roasting pan. Layer onion and lemon slices over ribs. Season with salt and pepper. Cover with aluminum foil and bake for 1 hour and 20 minutes to 1 hour and 30 minutes or until ribs are tender. Set aside.
Meanwhile, in a medium sauce pan sauté onions and garlic in oil until onion has softened. Add remaining ingredients and simmer for 5 minutes.
Prepare outdoor grill with medium coals, or heat gas grill to medium.
If needed, heat remaining sauce for dipping and serve with ribs.
To Broil: Heat broiler. Brush rubs with sauce. Place on greased broiler-pan rack. Broil 8 minutes. Turn ribs over; brush with more sauce. Broil for 7 minutes or until crisped.
Servings: 6