Prepare the Ingredients : Slice tomatoes and mozzarella. Wash and pat dry fresh basil leaves.

Assemble the Panini : Spread 1 tablespoon pesto on one side of each bread slice. On two slices, layer mozzarella, tomato slices, and fresh basil. Season with salt and black pepper. Top with remaining bread slices, pesto side down.

Heat the Panini : Preheat a panini press or skillet over medium heat. Brush the outside of the sandwiches with olive oil or melted butter.

Grill the Sandwiches : Place sandwiches in the panini press or skillet. Cook for 4–5 minutes on each side (or until using a press, follow manufacturer instructions) until bread is golden and crispy and cheese is melted.

Serve : Remove from heat and let rest for 1–2 minutes. Slice in half and serve immediately.