Preheat your oven to 375°F (190°C).
Poach the chicken breast in simmering water for 12-15 minutes until fully cooked, then shred using two forks.
In a small saucepan, heat the olive oil over medium heat and stir in the chili powder, cumin, garlic powder, and sea salt for 30 seconds until fragrant.
Pour the tomato puree into the spice mixture and simmer for 5 minutes to allow the flavors to meld into a rich red sauce.
Sauté the diced red onion and bell pepper in a non-stick skillet until softened, then toss them with the shredded chicken and 2 tablespoons of the prepared sauce.
Briefly warm the corn tortillas in a dry pan to make them pliable, then fill each with the chicken mixture and roll tightly.
Place the rolled tortillas seam-side down in a small baking dish, top with the remaining red chili sauce, and sprinkle with the shredded cheddar cheese.
Bake for 15 minutes until the sauce is bubbling and the cheese has melted, then garnish with fresh cilantro before serving.