Place bread slices on a cutting board and butter each slice with softened butter. Place bread butter-side down on cutting board.

Spread 1-2 tablespoons pesto on half of bread slices and begin layering mozzarella, gouda, and Parmesan on top of pesto. Top with tomato slices and season tomatoes with salt and pepper to taste.

Working in batches, cook grilled cheese in a large nonstick skillet over medium heat 3-4 minutes per side until grilled cheese is golden brown and cheese is melted. Repeat cooking with remaining grilled cheese.

Serve grilled cheese immediately warm and enjoy!