I've been doing these for a few years whenever I need something really quick to eat.
I use medium sized tortillas but others would work too
take a tortilla and spread some ketchup and tobasco on it (like you would on a pizza) cover one half of it generously with shredded cheese. fold in half. place in toaster oven for about 3 minutes at 400F. Enjoy.
I've also done them with BBQ sauce.
variations include pepperoni or salami slices