In a large skillet over medium heat, sauté the sliced onion and bell peppers until they are softened, about 5-7 minutes.
Add the shredded chicken to the skillet, followed by the fajita seasoning, black beans, corn, and salsa. Mix everything well and cook for an additional 3-4 minutes until heated through.
In a separate bowl, combine sour cream and half of the shredded cheddar cheese, mixing until smooth.
In a greased 9x13 inch baking dish, layer half of the chicken mixture on the bottom, followed by half of the crushed tortilla chips.
Spread the sour cream and cheese mixture evenly over the tortilla chips. Then add the remaining chicken mixture on top.
Finally, sprinkle the rest of the crushed tortilla chips over the chicken, and top with the remaining cheddar cheese.
Bake in the preheated oven for about 25-30 minutes, or until the casserole is bubbly and golden on top.
Remove from the oven and let it cool slightly before serving.
Garnish with chopped cilantro before serving.
Notes
Let the casserole cool slightly before serving for better slicing.