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 each breast 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 top surface.
04 - Bake chicken for 15 minutes until lightly browned and partially cooked through.
05 - While chicken bakes, combine diced tomatoes, red onion, minced garlic, chopped basil, extra-virgin olive oil, balsamic vinegar, salt, and pepper in a medium bowl. Toss thoroughly to combine and set aside to allow flavors to meld.
06 - Remove chicken from oven after 15 minutes. Top each breast with one-quarter of the bruschetta mixture, then sprinkle shredded mozzarella evenly over all pieces.
07 - Return to oven and bake for 8-10 minutes until chicken reaches internal temperature of 165°F and cheese is melted and bubbly with slight browning.
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 or on the side.