Preheat oven to 350°F (175°C).
In a large skillet, heat olive oil over medium heat. Add the diced onions and cook until translucent.
Stir in the shredded chicken, black beans, corn, cumin, garlic powder, and salt. Mix until heated through.
Spread a thin layer of green enchilada sauce on the bottom of a 9x13 inch baking dish.
Layer the first five corn tortillas over the sauce.
Top the tortillas with half of the chicken mixture, followed by a sprinkle of cheese.
Add another layer of tortillas, repeat with the remaining chicken mixture and cheese.
Top with remaining tortillas and pour the remaining enchilada sauce over the top, then sprinkle with cheese.
Cover with foil and bake for 25 minutes, then uncover and bake for an additional 15 minutes.
Let stand for 10 minutes before serving.