How can I clean the ceiling of a toaster oven?

Are there heating coils in the “ceiling” there? If they can be removed, I would do so.

That’s how I clean my regular oven.

I would try using an SOS pad or something like Soft Scrub, to help remove the oxidized spots.

I also line my toaster & regular oven with aluminum foil, even up the sides.

In the future Perhaps you can put foil loosely on the food for the first half of their cooking in the oven?

I recently cleaned my convection toaster oven. I was only cleaning grease off the bottom crumb pan, but it didn't respond to my usual degreaser cleansers. I bought Krud Kutter from the paint department (not the cleaning supplies dept.) at a home improvement store. I soaked the crumb tray then used a mesh scouring pad to scrub. http://ak1.ostkcdn.com/images/products/P12257817.jpg It took repeated soaking and scrubbing over two days to get it clean.

Be careful with the scouring pad. My normal scrub sponge was totally ineffective. I then tried my stainless steel scouring pad which immediately scratched the metal. I then bought the poly mesh pad which required more elbow grease but didn't scratch the surface. My oven uses quartz heating elements which should never have cleanser applied to them. Ideally, cleaning should be done weekly, but check for spatters after roasting or broiling and clean as soon as possible.

I'd try a magic eraser on the top to see if that will clean off the baked on gunk.

I use a hot wet rag or sponge, and then use a round plastic scrubby to get the baked on bits off. Repeat wet rag as needed.

Unplug it remove rack turn it upside down spritz with water then sprinkle baking soda on it until pasty then let sit for 1 hr. Wipe with damp rag and should wipe up nice and clean but if still remaining crud repeat process.