Add salt, black pepper, onion powder, chili powder, cumin, garlic powder, and smoked paprika to a small bowl. Mix together to combine and set aside.
Line a large cutting board with plastic wrap or parchment paper. Lay chicken breasts on top in a single layer, and then cover with another piece of plastic wrap or parchment paper.
Using a meat mallet or a heavy skillet (cast iron works best), pound each breast to about 3/4-inch thickness.
Sprinkle the seasoning mix evenly on both sides of the chicken breasts.
Pour 1 cup of salsa onto the bottom of the baking dish and spread out evenly.
Place chicken breasts on top and spoon the remaining salsa on each one.
Bake for 35 minutes, or until chicken is tender, juicy, and fully cooked through. (The internal temperature should read 165ºF with a meat thermometer.)
Remove from oven and sprinkle the top of each chicken breast with cheese.
Turn the oven broiler on high, place chicken under the broiler, and broil for 1-2 minutes, or until the cheese is melted and bubbly.
Remove from oven, let cool for 5 minutes, and serve.
Notes
Cheese: Cheddar, Monterey Jack, Mozzarella, or a Mexican-blend shredded cheese all work in this recipe!