I have taken dishwasher soap, powdered or liquid and poured a big lot of it in the pan and then added some water to it, enough so that you can boil it for a while. Then let it cool in the solution and you should be able to get it off with a scratcher without much effort. I always cleaned my stove burner pans like this before I had the flat top. You may have to do this a couple of times, but don't be stingy with the dishwasher soap. You probably will think you have added way to much, but then add some more. Good luck