Gather your ingredients: bread, butter, mozzarella cheese, pizza sauce, pepperoni (if using), Italian seasoning, and garlic powder.
Spread 1 tablespoon of softened butter on one side of each slice of bread.
Place one slice of bread, buttered side down, in a preheated skillet over medium heat. Sprinkle half of the shredded mozzarella cheese over the bread, then spread the pizza sauce on top. If using, layer the pepperoni, followed by the remaining mozzarella cheese, Italian seasoning, and garlic powder.
Top with the second slice of bread, buttered side up. Cook for about 3-4 minutes until golden brown, then flip and cook for another 3-4 minutes until the other side is golden brown and the cheese is melted.
Remove from skillet, let cool for a minute, cut in half, and serve warm.