From what you described, it's probably burned, not a stain. Try using a Mr. Clean Eraser-it's slightly abrasive and may help. I have a self-cleaning oven I hate. It gets so hot during the cleaning process it gives off smoke/fumes. and once I made the mistake of leaving a cloth potholder on the stove during the cleaning cycle and it caught on fire. I prefer to use Easy Off cleaner to clean my oven.