Bring the baking soda or cream of tartar and vinegar solution to a boil on the stove. Pour the solution into the stained bakeware to cover the stains. Allow the vinegar mixture to remain in the bakeware until it's completely cool.
Pour most of the solution out of the bakeware, leaving enough to cover the bottom of the pan. Roll an old nylon stocking into a ball. Scrub the stained areas of the nonstick bakeware with the nylon to loosen the stains.
Rinse the bakeware with water. Dry the bakeware completely with a kitchen towel.
Dry your nonstick bakeware after washing by hand and place cardboard or a thin towel between pans to avoid scratching the coating.
The coating on nonstick bakeware and cookware can be scratched in the dishwasher. Wash your nonstick items by hand.