Preheat your oven to 375°F (190°C).
In a small bowl, whisk together the tomato puree, chili powder, cumin, garlic powder, and sea salt to create the enchilada sauce.
Finely dice the red onion and sauté it in a non-stick skillet with a tablespoon of water until softened, then toss with the shredded cooked chicken breast.
Warm the corn tortillas slightly in the microwave or on a dry skillet so they are pliable and do not crack.
Spread 2 tablespoons of the red sauce on the bottom of a small baking dish.
Dip each tortilla into the sauce bowl to coat both sides, fill with the chicken and onion mixture, then roll tightly and place seam-side down in the dish.
Pour the remaining sauce over the top of the tortillas and sprinkle evenly with the shredded cheddar cheese.
Bake for 15-18 minutes until the sauce is bubbling and the cheese has melted perfectly.
Remove from the oven and garnish with freshly chopped cilantro before serving.