We burned some onions really badly in my Le Creuset Dutch oven. Tried vinegar, baking soda, etc. then read that you should use hydrogen peroxide and baking soda. I did this a couple of times, then hit it with some of that super Dawn. The stain came off, but the shiny surface is gone on the bottom and what is left is a dull white rough surface that stains when anything is cooked in it. Is this safe to cook with? Or was the operation a success but the patient died?