Preheat your oven to 375°F (190°C).
Poach or pan-sear the chicken breast until fully cooked, then shred it with two forks.
In a small skillet, heat the olive oil over medium heat and sauté the diced onions until translucent.
In a small bowl, whisk together the tomato puree, chili powder, cumin, garlic powder, sea salt, and black pepper to create the red chili sauce.
Warm the corn tortillas in a dry pan for 30 seconds per side to make them pliable.
Dip each tortilla into the red chili sauce to coat lightly, then fill with the shredded chicken and sautéed onions.
Roll the tortillas tightly and place them seam-side down in a small baking dish.
Pour the remaining chili sauce over the top of the tortillas and sprinkle with the shredded cheddar cheese.
Bake for 15-20 minutes until the sauce is bubbling and the cheese is melted.
Garnish with fresh cilantro before serving.