Dice onions, peppers, and olives and set aside.
Heat olive oil in a large skillet. Add onions and salt and sauté for 3-4 minutes or until onions are translucent. Add bell peppers and cook for another 4-5 minutes. Bell peppers should be slightly tender but still have crunch.
Remove from heat. Add garlic and onion powders, corn, beans, and olives to pepper mixture and stir well to combine.
Pour a portion of enchilada sauce into an oven-safe 9x13 baking dish, spreading so entire base is covered. Lay a single layer of tortillas along the base of the dish, overlapping as necessary. Spread another thin layer of sauce on top of the tortillas. Portion half of the pepper mixture onto the tortillas and spread evenly. Sprinkle a light layer of cheese on top. Layer with another round of tortillas and repeat the pepper mix and cheese. Add a final layer of tortillas, and cover with additional sauce, cheese, olives, and any other preferred garnish.
Bake covered at 350° for 25 minutes. Remove aluminum foil and bake for another 10-15 minutes or until cheese is golden and bubbly. Wait at least 10 minutes prior to slicing and serving.
Note: Additional sauce may be used in the middle layer of tortillas, however, casserole may become soggy (although still delicious!). We found using sauce on the bottom and top layers only achieved our preferred result.