Preheat your oven to 375°F.
Poach the chicken breast in a pot of simmering water for 12 minutes or until fully cooked through.
Remove the chicken from the water and shred it using two forks, then place it in a medium mixing bowl.
In a small saucepan over medium heat, whisk together the tomato puree, chicken broth, ancho chili powder, cumin, garlic powder, onion powder, sea salt, and black pepper.
Simmer the sauce for 5 minutes until slightly thickened, then stir 2 tablespoons of the sauce and the diced yellow onion into the shredded chicken.
Warm the corn tortillas in a dry skillet over medium heat for 30 seconds per side until they are soft and pliable.
Dip each tortilla into the remaining sauce to coat, fill with the chicken mixture, roll tightly, and place seam-side down in a small baking dish.
Pour the rest of the ancho chili sauce over the top of the rolled tortillas and sprinkle evenly with the shredded cheddar cheese.
Bake for 15 minutes until the sauce is bubbling and the cheese has completely melted.
Garnish the hot enchiladas with fresh chopped cilantro before serving.