Preheat your oven to 375°F (190°C).
Poach the chicken breast in simmering water for 12-15 minutes until cooked through, then shred with two forks.
Heat olive oil in a skillet over medium heat and sauté the diced onion and bell pepper until softened, about 5 minutes.
In a bowl, combine the shredded chicken, sautéed vegetables, sea salt, black pepper, and chili powder.
Spread 2 tablespoons of enchilada sauce on the bottom of a small baking dish.
Briefly warm the corn tortillas in a dry pan to make them pliable.
Fill each tortilla with the chicken mixture, roll tightly, and place seam-side down in the baking dish.
Pour the remaining enchilada sauce over the tortillas and sprinkle with shredded cheddar cheese.
Bake for 15-20 minutes until the cheese is melted and the sauce is bubbling.
Garnish with fresh chopped cilantro before serving.