Preheat your oven to 375°F (190°C).
In a small skillet, heat olive oil over medium heat and sauté the diced bell pepper and red onion until softened, about 5 minutes.
Poach the chicken breast in simmering water until cooked through, then shred it using two forks.
In a medium bowl, whisk together the tomato puree, Greek yogurt, chili powder, cumin, garlic powder, sea salt, and black pepper to create the creamy enchilada sauce.
Toss the shredded chicken and sautéed vegetables with half of the creamy sauce until well coated.
Cut the corn tortilla into quarters. In a small oven-safe baking dish, place half of the tortilla pieces at the bottom.
Spread the chicken and vegetable mixture over the tortillas, then top with the remaining tortilla pieces and the rest of the sauce.
Sprinkle the shredded cheddar cheese over the top and bake for 15-20 minutes until the cheese is melted and the sauce is bubbling.