Preheat your oven to 375°F (190°C). This will ensure that your casserole bakes evenly.
In a large mixing bowl, combine the shredded chicken, fat-free sour cream, reduced-fat cheddar cheese, ground cumin, chili powder, kosher salt, and ground black pepper. Mix until everything is well combined.
Fold in the corn kernels and black beans into the chicken mixture. This adds a wonderful texture and nutrient boost to your casserole.
Spread a thin layer of the chicken mixture on the bottom of your greased baking dish. Place one tortilla over the mixture, then layer more chicken mixture on top. Repeat the layering process until you run out of tortillas and filling, finishing with a layer of chicken mixture on top.
Cover the baking dish with aluminum foil and place it in the preheated oven. Bake for 25 minutes. After 25 minutes, remove the foil and bake for an additional 10-15 minutes, or until the top is golden and bubbly.
Once baked, take the casserole out of the oven and let it cool for about 10 minutes. This will help it set and make it easier to cut into squares.