Stir together dry ingredients in a small bowl. Reserve 3 tbsp. of mixture. Sprinkle remaining mixture over both sides of the ribs and rub it in.

Place ribs in baking dish. Cover and chill 2 to 24 hours.

When ready to grill, place ribs, bone sides down, on lightly greased grill, over a medium flame. Cover and grill for 1 1/2 to 1 3/4 hours, or until ribs are tender.

While ribs are cooking, heat oil in a saucepan over medium heat. Stir in onion and cook until tender, about 5 minutes. Stir in remaining ingredients, along with reserved spice mixture. Simmer, uncovered, until sauce is thickened and reduced to about 1 1/2 cups liquid, about 20 minutes, stirring occasionally.

When ribs are nearly finished cooking, about the last 5 minutes, brush generously with sauce.

Remove ribs from grill and cut into serving portions. Serving with remaining sauce.