Step 1

Preheat oven to 375℉. Spray an 8"x8" baking pan with nonstick spray.

Step 2

Bring a skillet sprayed with nonstick spray to medium-high heat. Add onion, salt, and pepper. Cook and stir until slightly softened, about 3 minutes.

Step 3

Transfer onion to a large bowl. Add cream cheese, 1/4 cup shredded cheese, chicken, and taco seasoning. Mix until uniform. Fold in diced tomatoes with chiles.

Step 4

Transfer half of the chicken mixture to the baking pan, and smooth out the surface. Add half of the tortilla pieces in an even layer, and top with 1/4 cup shredded cheese. Repeat layering with remaining chicken mixture, tortilla pieces, and 1/4 cup shredded cheese.

Step 5

Cover with foil, and bake for 25 minutes.

Step 6

Remove foil, and bake until entire dish is hot and bubbly and cheese has lightly browned, about 5 minutes.