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, black pepper, and Italian seasoning. Place seasoned chicken in the prepared baking dish.
03 - Spoon 1 tablespoon of basil pesto over each chicken breast, spreading evenly to cover the surface.
04 - Bake chicken for 15 minutes to begin cooking through.
05 - While chicken bakes, combine diced tomatoes, red onion, minced garlic, chopped fresh 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 evenly with one-quarter of the bruschetta mixture, then sprinkle shredded mozzarella over the top.
07 - Return to oven and bake for 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. Spoon any remaining bruschetta mixture over the top or serve on the side.