Preheat your oven to 375°F (190°C).
Heat the avocado oil in a small saucepan over medium heat, then add the diced white onion and sauté until translucent and aromatic.
Whisk in the tomato sauce, ancho chili powder, garlic powder, onion powder, ground cumin, and sea salt, allowing the sauce to simmer for 5 minutes to develop flavor.
In a medium mixing bowl, combine the cooked shredded chicken breast with 2 tablespoons of the warm ancho sauce until evenly coated.
Briefly warm the corn tortillas in a dry pan or microwave to make them pliable, then dip each tortilla into the remaining sauce.
Fill each sauce-dipped tortilla with the chicken mixture, roll them tightly, and place them seam-side down in a small baking dish.
Pour any remaining ancho sauce over the top of the tortillas and sprinkle evenly with the shredded sharp cheddar cheese.
Bake for 15 minutes until the cheese is melted and bubbling, then garnish with fresh cilantro before serving.