Begin by dicing the onion and bell peppers into small pieces. Rinse and drain the black beans to remove excess sodium. If you're using fresh chicken breasts, ensure they are trimmed of any excess fat.

In the slow cooker, start by placing a layer of gluten-free tortillas at the bottom. Layer this with bits of chicken, followed by a generous drizzle of enchilada sauce, a handful of black beans, and a sprinkle of cheddar cheese. Repeat the layering process until all ingredients are used, ensuring the top layer finishes with cheese.

Cover the slow cooker and set it to cook on low heat for approximately 5 hours. You'll know it's ready when the chicken reaches an internal temperature of 165°F and the cheese on top is bubbly.

For an added touch of texture, you might want to broil the casserole briefly after cooking. Transfer the top layer to an air fryer or a preheated oven and broil for about 3–5 minutes until the cheese is golden.

Once cooked, carefully scoop out portions of the casserole onto plates, serving warm with fresh cilantro and a dollop of sour cream.