Place two buttered bread slices (buttered side down) in skillet. Place 1-2 slices of cheddar, provolone, and tomato, along with pinch of salt and pepper, on top of bread, and top with remaining buttered sourdough.
Cook for around 4-5 minutes or until bottom turns golden brown. Flip over sandwich and cook another 4-5 minutes, until other side is golden brown. Serve warm.
Go low and slow. Be patient with your grilled cheese. If it looks like your cheese isn't melting after a few minutes, cover the pan for a minute or two to help it along.
How to reheat: I recommend reheating it in the toaster oven (or regular oven) to help re-crisp the bread. Place it in a 350 degree F oven for around 10 minutes. Reheating in the microwave may lead to soggy bread.