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 evenly with olive oil, then sprinkle with salt, black pepper, and Italian seasoning on all sides. Place seasoned chicken in the prepared baking dish.
03 - Spoon 1 tablespoon of basil pesto over each chicken breast and spread evenly across the surface using the back of the spoon.
04 - Place baking dish in preheated oven and bake for 15 minutes.
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 mixing 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 cheese evenly over all pieces.
07 - Return dish to oven and bake for an additional 8–10 minutes, until chicken reaches an internal temperature of 165°F and cheese is melted and lightly golden.
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.