Season the chicken breasts: Pat the chicken breasts dry with paper towels. Season both sides with salt, black pepper, crushed garlic, and Italian herbs. Let them sit for 5 minutes to absorb the flavors.

Sear the chicken: Heat the olive oil in a large skillet over medium-high heat. Add the chicken breasts and sear for 3-4 minutes on each side, or until golden brown. Remove the chicken from the skillet and set aside.

Make the sauce: In the same skillet, add the finely chopped onion and sauté for 2-3 minutes until softened. Stir in the marinara sauce and cook for another minute. Let the sauce simmer for 5 minutes, allowing the flavors to meld.

Cook the chicken: Return the chicken breasts to the skillet, nestling them into the tomato sauce. Reduce the heat to medium-low, cover, and let the chicken cook for 10-12 minutes, or until fully cooked (internal temperature of 165°F or 74°C).

Finish the dish: Scatter the halved cherry tomatoes over the top. Sprinkle the shredded mozzarella cheese evenly over the chicken and tomatoes. Cover the skillet again and let it sit for 2-3 minutes, just until the cheese melts.

To serve: Remove the skillet from the heat. Tear the fresh basil leaves and scatter them over the dish. Serve immediately, pairing it with a fresh green salad.