Preheat the oven to 400°F and position a rack in the middle.

Place the chicken breast flat on a cutting board and slice horizontally to create cutlets.

Pat the chicken breast cutlets dry and season with kosher salt and black pepper.

In a 9x13 baking dish, add about 3 tablespoons extra virgin olive oil, juice of 1 lemon, chicken broth, rosemary, and minced garlic. Mix to combine.

Add the chicken breast cutlets to the baking dish and toss to coat with the olive oil and garlic mixture, then add the onion slices and toss again.

Cover the baking dish with foil and bake for 10 minutes.

Remove the foil and return the baking dish to the oven for another 10 to 15 minutes or until the chicken is fully cooked.

Remove the chicken from the oven when the internal temperature reaches 160°F. Let rest for 5 minutes.

Garnish with lemon slices and squeeze juice from the remaining lemon over the chicken.