Preheat the oven to 375 degrees.
Start by putting together the bruschetta tomato mixture. Mix the tomatoes, onions, garlic, olive oil, and balsamic vinegar in a large bowl. Set it aside.
Next prepare the chicken. Trim off any excess fat or skin for the boneless chicken breasts. Then, one at a time, place them in between two pieces of plastic wrap or into a plastic Ziploc bag and, using a meat mallet, pound the chicken breasts into ½ inch thick pieces. You want the chicken breasts to be relatively the same size, so they cook evenly.
In a small dish, mix the Italian seasoning, onion powder, garlic powder, salt, and pepper. Season the chicken breasts with the seasoning mixture.
Place the seasoned chicken breasts into a 9 x13 ceramic baking dish.
Pour the bruschetta on top of the chicken and then place it in the oven for 45 - 50 minutes. The internal temperature of the chicken should read 165 degrees Fahrenheit when it’s cooked thoroughly.
Remove the chicken bruschetta bake from the oven, and sprinkle with fresh basil. Serve hot with pasta, rice, zoodles, or spaghetti squash.