01 - Preheat oven to 400°F. Lightly grease a baking dish or sheet pan with cooking spray or olive 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 on both sides. Place seasoned chicken in the prepared baking dish.
03 - Spoon 1 tablespoon basil pesto over each chicken breast, spreading it evenly to cover the top surface.
04 - Place baking dish in preheated oven and bake for 15 minutes to partially cook the chicken.
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 with one-quarter of the bruschetta mixture, distributing evenly. Sprinkle shredded mozzarella cheese over the top of each breast.
07 - Return baking dish to oven and bake for an additional 8-10 minutes, until chicken is cooked through (internal temperature reaches 165°F) and cheese is melted and lightly bubbly.
08 - Let chicken rest for 3-5 minutes before serving to allow juices to redistribute. Serve with any remaining bruschetta mixture spooned over the top or on the side.