In a large skillet, heat olive oil over medium heat. Add onion and garlic and cook for 3-4 minutes, stirring occasionally, until softened.
Add chili powder, cumin, salt, and pepper and stir to combine. Add chicken, black beans, and corn and cook for an additional 5 minutes.
Remove from heat and let cool slightly. Preheat oven to 350°F.
In a greased 9x13 inch baking dish, spoon 1/2 cup of salsa over the bottom. Place 1/4 cup of the chicken mixture in the center of each tortilla, top with 2 tablespoons of cheese, and roll up. Place seam-side down in the baking dish.
Pour remaining salsa and cheese over the top of the enchiladas. Cover with aluminum foil and bake for 25 minutes.
Remove foil and bake for an additional 5 minutes. Serve with a dollop of sour cream and fresh cilantro, if desired.