Try a paste of baking soda. Let it sit on it for a while and then scrub with it. It won't scratch that surface. Otherwise, you might want to go the all-out approach and use an oven cleaning application on it. I never clean the oven, so I don't know what to recommend, but those are meant to remove that kind of stuff. Obviously if heat is involved you'll have to figure that one out. Cook some thing and let it radiate heat to the burner? Find one that doesn't have toxic fumes.
Phone is working again, so I can go back to my rewiring. They were working on them up the street yesterday and left mine disconnected at the big gray box.