Step 1

Preheat oven to 375°F. Spray an 8"×8" baking pan with nonstick spray.

Step 2

Add chicken to the baking pan, and season with 1 tsp. taco seasoning and 1/2 tsp. garlic powder. Top with onion and pepper.

Step 3

Place 1/2 cup Mexican-blend cheese in a large microwave-safe bowl. Add sour cream, cream cheese, and remaining 1 tsp. taco seasoning and 1/2 tsp. garlic powder. Mix well. Microwave for 1 minute, or until cheese has melted. Mix until smooth and uniform.

Step 4

Add diced tomatoes with chiles to the bowl, and stir well. Transfer mixture to the baking pan, and smooth out the top. Cover with foil, and bake for 20 minutes.

Step 5

Remove foil, and top with remaining 1/2 cup Mexican-blend cheese. Bake until cheese has melted and chicken is cooked through, about 10 minutes.