Gather all the ingredients on a clean surface.
Spread butter on one side of each slice of bread.
Place one slice of bread, butter side down, in a heated skillet.
Add the cheese slices on top of the bread in the skillet.
If using, layer any additional ingredients like ham or tomato on the cheese.
Top with the second slice of bread, butter side up.
Cook for about 3-4 minutes until the bottom is golden brown.
Carefully flip the sandwich with a spatula.
Cook for another 3-4 minutes until the cheese melts and the bread is golden.
Remove from heat, let cool slightly, then slice and serve.