Prep the oven and pan: Preheat your oven to 400°F (200°C). Lightly grease a baking dish or line a sheet pan with parchment for easy cleanup.
Flatten the chicken: Place chicken breasts between two sheets of plastic wrap and gently pound the thicker ends so each piece is even.
This ensures quick, even cooking and helps keep the meat juicy.
Season generously: Pat the chicken dry. Rub with 1 tablespoon olive oil, then season both sides with salt, black pepper, and oregano. Set aside while you make the bruschetta topping.
Make the bruschetta mixture: In a bowl, combine diced tomatoes, minced garlic, red onion (if using), 2 tablespoons olive oil, balsamic vinegar, basil, red pepper flakes (if using), and a pinch of salt and pepper.
Stir gently and taste. Adjust seasoning so it’s bright and well-balanced.
Pre-bake the chicken: Arrange chicken in the baking dish. Bake for 12–15 minutes, depending on thickness, until it’s nearly cooked through but not quite done.
Add mozzarella: Remove the chicken from the oven and top each piece with mozzarella.
Return to the oven for 5–7 minutes, or until the cheese is melted and the chicken reaches an internal temperature of 165°F (74°C).
Top with bruschetta: Spoon the tomato-basil mixture over the hot chicken. The warmth will release all the aromas and slightly soften the tomatoes without turning them mushy.
Finish and serve: Drizzle any remaining juices from the pan over the chicken. Sprinkle with extra basil and a little Parmesan if you like.
Serve immediately with your favorite sides.