Preheat your oven to 375°F (190°C).
In a small non-stick skillet, sauté the diced onion and bell pepper over medium heat until softened, about 5 minutes.
In a medium mixing bowl, combine the cooked shredded chicken breast, Greek yogurt, diced green chilis, ground cumin, chili powder, sea salt, and black pepper.
Spread 2 tablespoons of the red enchilada sauce on the bottom of a small oven-safe baking dish.
Place the corn tortilla on top of the sauce (you may cut it in half to fit the dish better).
Spread the chicken and yogurt mixture evenly over the tortilla.
Pour the remaining enchilada sauce over the chicken layer and sprinkle evenly with the shredded cheddar cheese.
Bake for 15-20 minutes, or until the sauce is simmering and the cheese has melted into a bubbly, golden crust.
Remove from the oven and let sit for 5 minutes before garnishing with fresh cilantro and serving.