Bake uncovered for 20 minutes with the baking sheet in the center of the oven.
After the 20 minutes, take the baking dish out carefully and cover with aluminum foil. Reduce oven temperature to 325° degrees and cook for 1 hour and 20 minutes. After the 1 hour and 20 minutes, remove ribs from the oven, remove foil and increase the oven temperature to 425° degrees. Place ribs back in the oven and cook for 20 minutes uncovered.