Have you tried oven cleaner? Or ammonia in a plastic garbage bag over night?
I would try covering it with baking soda and vinegar and letting that sit for a while. Then use a scouring pad to scrape it off.
Sheron....Have you tried Barkeepers Friend with a good brush?.
Hey Sheron: This always works for me: What I use is a paste of vinegar and cream of tartar (the dry stuff). Make a paste and put it on the gunk. Let it sit for about 15 or 20 seconds and then scrape off with a plastic putty knife or one of those plastic scrubbies. You may have to do it a couple of times if the gunk is thick, but usually not. There is no smell and it is environmentally safe. Good luck