Season chicken breasts with salt, pepper, and Italian seasoning.
Preheat the grill.
Meanwhile, make the bruschetta. Stir together chopped tomatoes, basil, salt, pepper, and lemon juice.
Once the grill is preheated, cook chicken breasts 5-6 minutes each side, basting generously with melted Lemon Herb Butter on both sides. Chicken should reach an internal temperature of 165° F when fully cooked.
Place a slice of mozzarella cheese on each breast and close the grill lid for 3-5 minutes, until the cheese is melted.
