Pat chicken dry. Place a chicken breast in a large zip-top bag and zip the top (make sure to release any air in the bag first), then place it on your poultry cutting board. Using a meat mallet like this one, pound to flatten the chicken. Repeat the process with the remaining chicken breast pieces.
Season the chicken with kosher salt and pepper on both sides and place in a large mixing bowl or dish. Add spices, minced garlic, extra virgin olive oil, and lemon juice. Combine to make sure the chicken is evenly coated with the spices and garlic.
In a large lightly oiled baking dish or pan, spread the onion slices on the bottom. Arrange seasoned chicken on top, and add the tomatoes.
Cover the baking dish tightly with foil and bake for 10 minutes covered, then uncover and bake for another 8 to 10 minutes or so. Watch carefully. This can take less or more time depending on the thickness of your chicken breasts. To be sure the chicken is cooked through, use an instant digital cooking thermometer. It should register 165 degrees F.
Remove from the heat. Let the chicken breasts rest (cover with foil or another pan) for 5 to 10 minutes or so before serving. Uncover and garnish with fresh parsley and basil. Enjoy!
Important Cook's Tips: Do not skip pounding the chicken (step #2). Pounding the chicken into thinner, and more evenly flat pieces helps it cook faster and more evenly. And by pounding the chicken breast, you're also mechanically tenderizing it, which means you'll end up with a juicer and tastier chicken dinner.
Cook's Tip: Let chicken rest before serving to allow juices to redistribute.