1. Pat the chicken dry with a paper towel. Place the chicken on a cutting board and cover it with a piece of plastic wrap. Use a mallet or rolling pin to gently pound the chicken to an even thickness (about 1/2" thick). This step is very important to make sure the chicken cooks quickly and evenly, without drying out.

2. Combine the chili powder, cumin, garlic powder, salt, and pepper in a small bowl. Sprinkle the spices over both sides of the chicken, and then rub it over the surface to make sure it's evenly coated.

3. Heat a large deep skillet over medium heat. Add the oil and swirl to coat the surface. Once the skillet is very hot, add the chicken and cook on both sides until browned and cooked through (about 5 minutes each side. Cooking time will vary with the size of your chicken pieces and type of cookware). 

4. Transfer the cooked chicken to a clean cutting board and let it rest while you prepare the sauce. Turn the burner down to medium low. Pour the salsa into the skillet and stir to dissolve the browned bits from the bottom of the skillet. Add the black beans and corn kernels and allow the sauce to heat through. Turn the heat off.

5. Slice the chicken breast into strips, then place it on top of the salsa sauce in the skillet. Top the skillet with crumbled cheese and cilantro or green onion. Serve over a bed of cooked rice.