01 - Preheat oven to 400°F. Lightly grease a baking dish or sheet pan with cooking spray or a small amount of olive oil.
02 - Pat chicken breasts dry with paper towels. Rub each breast with olive oil, then sprinkle evenly with salt, black pepper, and Italian seasoning on both sides. Place seasoned chicken in the prepared baking dish.
03 - Spoon 1 tablespoon of basil pesto over each chicken breast, spreading it evenly to cover the top surface.
04 - Place baking dish in the preheated oven and bake for 15 minutes.
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 mixing bowl. Toss thoroughly to combine all ingredients and set aside to allow flavors to meld.
06 - After 15 minutes, remove chicken from oven. Top each breast with one-quarter of the bruschetta mixture, then sprinkle shredded mozzarella evenly over the topped chicken.
07 - Return dish 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 golden.
08 - Let chicken rest for 3 to 5 minutes before serving to allow juices to redistribute. Serve with any remaining bruschetta topping spooned over the top or on the side.