01 - Preheat oven to 400°F. Lightly grease a baking dish or sheet pan with cooking spray or a small amount of oil.
02 - Pat chicken breasts dry with paper towels. Rub each breast with olive oil, then season evenly with salt, pepper, and Italian seasoning on both sides. Place in the prepared baking dish.
03 - Spoon 1 tablespoon of basil pesto over each chicken breast, spreading it evenly to coat the top 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, salt, and pepper in a medium bowl. Toss well to combine and set aside to let flavors meld.
06 - Remove chicken from the oven after 15 minutes. Top each breast with a quarter of the bruschetta mixture, then sprinkle shredded mozzarella evenly over all pieces.
07 - Return to oven and bake for another 8 to 10 minutes, until chicken is cooked through (internal temperature reaches 165°F) and cheese is melted and lightly browned.
08 - Let chicken rest for 3 to 5 minutes before serving. Serve with any remaining bruschetta topping spooned over the top or on the side.