Preheat your oven to 350°F (175°C).
In a large skillet, melt the butter over medium-high heat. Add the chopped onion and sauté for 3-4 minutes until translucent.
Mix in the almond flour and cook for another 1-2 minutes until slightly thickened.
Pour in the chicken broth and stir well, cooking for an additional 3-4 minutes until the sauce thickens.
Incorporate the sour cream and salsa, then remove from heat.
Stir in the chicken, 6 oz of shredded cheddar cheese, and tortilla pieces.
Transfer the mixture to a cooking spray-coated 8x8-inch dish and top with the remaining 2 oz of cheddar cheese.
Cover and bake for 20 minutes, then uncover and bake for another 15 minutes.
Allow to cool for 10 minutes before serving.