01 - Preheat oven to 400°F. Lightly grease a baking dish or sheet pan with cooking spray or oil.
02 - Pat chicken breasts dry with paper towels. Rub with olive oil, then season evenly with salt, pepper, and Italian seasoning. Place seasoned chicken in the prepared baking dish.
03 - Spoon 1 tablespoon basil pesto over each chicken breast, spreading evenly to cover the surface.
04 - Bake chicken for 15 minutes in the preheated oven.
05 - While chicken bakes, combine diced tomatoes, red onion, minced garlic, chopped basil, extra-virgin olive oil, balsamic vinegar, ½ teaspoon salt, and ¼ teaspoon black pepper in a medium bowl. Toss well and set aside to marinate.
06 - Remove chicken from oven after 15 minutes. Top each breast with a quarter of the bruschetta mixture, then sprinkle evenly with shredded mozzarella cheese.
07 - Return to oven and bake for another 8-10 minutes, until chicken reaches internal temperature of 165°F and cheese is melted and bubbly.
08 - Let chicken rest for 3-5 minutes before serving to allow juices to redistribute. Serve with any remaining bruschetta topping spooned over the top.