Marinate the chicken breasts for at least 24 hours in a ziploc bag.
Preheat the oven to 375 degrees. Prepare and spray the bottom and sides of a 9×13 pan. Layer green beans, sliced, onion, and fresh corn.
Lay the chicken breasts on top of the corn. Sprinkle with chopped cilantro. Cover with foil and bake for 35-40 minutes, or until the chicken breast is done. (Depending on the thickness of the chicken breast.)
Remove the foil and top with more fresh cilantro and chopped tomatoes. Serve!