Preheat oven to 350°F. Spray a 13x9-inch (or similar) baking dish with cooking spray.
Bring a large pot of heavily salted water to a boil. Cook the pasta for 2 minutes less than the package directions. Drain and rinse with cold water.
In a large mixing bowl, combine the shredded chicken, cream cheese, onion, and chopped chiles, and stir until combined.
Add the enchilada sauce and 1 cup of the grated cheese. Stir and pour into the prepared baking dish.
Cover with foil and bake for 20-25 minutes or until bubbly around the edges. Remove foil, sprinkle with remaining cheese, and bake for another 5 to 7 minutes or until the cheese is melted.
To prepare the optional topping, combine the tomatoes, cilantro, lime juice, with a drizzle of olive oil, and salt and pepper to taste. Serve as a topping for the casserole.