Combine the boneless, skinless chicken breasts with fajita seasoning in a bowl, ensuring it's well-coated. Heat 1 tablespoon of olive oil in a skillet over medium heat and cook the chicken for about 5-7 minutes until no longer pink. Remove from skillet and set aside.

In the same skillet, add more olive oil if needed, then sauté chopped onions and sliced bell peppers for 8-10 minutes until softened.

In a mixing bowl, blend together the softened cream cheese, condensed cream of chicken soup, diced tomatoes and green chilies, and sour cream until smooth. Stir in half of the shredded cheeses.

Preheat your oven to 350°F. Grease a baking dish and start layering with cream cheese mixture, corn tortillas, chicken and veggies, and more cream cheese mixture until all are used.

Cover with foil and bake for 25 minutes, then remove foil and bake for an additional 10-15 minutes until cheese is golden brown.

Let it cool for 10-15 minutes before slicing and serve with optional toppings like salsa, guacamole, or sour cream.