Butter the two slices of bread, then on the non-buttered side of one add the tomato, cheddar cheese and mozzarella cheese. Make sure the cheese slice cover the whole size of the bread slice, otherwise add multiple slices to ensure it is completely covered. Season to taste with salt and pepper.
Toast until the bread is brown and the cheeses are melted.
Let it cool for a minute or two before eating so you don't burn your mouth.