Add a few tomato slices, a few basil leaves, some black pepper to taste, another mozzarella layer and another bread slice with the buttered side up.
1 tomato, Black pepper to taste, A few leaves of fresh basil
Heat a pan on medium heat, place the sandwich inside, and cook for a few minutes. When the bread gets brown and crispy, carefully flip the sandwich on the other side. Bake for a few more minutes until the cheese has melted.
Repeat the same process for the other sandwich and serve them warm.