Add the enchilada sauce, sour cream, and taco seasoning to a large mixing bowl. Whisk to combine.
Add the chicken, yellow pepper, and jalapeno pepper to the sauce mixture and toss to coat completely. Set aside.
In another mixing bowl, combine the steamed cauliflower, cheese, coconut flour, egg, and taco seasoning, mix to combine well.
Transfer the cauliflower mixture to a 9x13 baking dish. Press with a spatula to cover the bottom of the baking dish.
Top the cauliflower mixture with the chicken mixture, distributing it evenly.
Sprinkle with the cheese and place in the oven to bake for 20 minutes. Remove the casserole from the oven and top with jalapeno slices (if using). Return to the oven for 10 minutes, or until the cheese has lightly browned.
Serve with tomato, cilantro, black olives, avocado ( if using).