Preheat your oven to 375°F and lightly grease a small baking dish.
In a small skillet, heat the avocado oil over medium heat and sauté the diced yellow onion until translucent and fragrant.
In a bowl, whisk together the tomato puree, chili powder, ground cumin, garlic powder, sea salt, and black pepper to create a smooth red sauce.
Combine the shredded chicken breast with the sautéed onions and 2 tablespoons of the prepared red sauce in a mixing bowl.
Briefly warm the corn tortillas in a dry pan or microwave to make them pliable, then fill each with the chicken mixture.
Roll the tortillas tightly and place them seam-side down in the baking dish, then pour the remaining sauce evenly over the top.
Sprinkle with the shredded cheddar cheese and bake for 15 to 20 minutes until the sauce is bubbling and the cheese is melted.
Remove from the oven and garnish with fresh cilantro before serving.