Combine first 6 ingredients in a heavy saucepan. Cook slowly over medium-low heat for 5 minutes, stirring occasionally. Pour sauce into a large bowl and let cool. Sauce can be prepared 24 hours ahead, covered and refrigerated. Preheat oven to 350 degrees. Season rib racks with salt and pepper. Arrange on a large baking sheet. Bake for 35 minutes Cool for 15 minutes. Cut racks into individual ribs. Add ribs to the sauce in the bowl and turn them to coat. Return ribs to baking sheet Bake 15 minutes longer, basting three times with remaining sauce.