Spread the butter evenly on one side of each slice of bread. If you’re using a panini press or nonstick pan, set the heat to medium heat.
Place one slice of bread, buttered side down, into the pan. Add the cheese slices on top. Use enough for full coverage. Next, layer on the tomato slices and top with a few fresh basil leaves.
Top with the second slice of bread, buttered side up. Cook on medium heat until the first side is golden brown, about 3 minutes. Flip carefully and cook until the other side is also golden brown, another 2-3 minutes.
Remove from the pan, let it cool slightly, and enjoy.