Preheat your oven to 375°F (190°C) and lightly grease a small oven-safe baking dish.
Dice the chicken breast into small, uniform bite-sized pieces.
Heat the olive oil in a skillet over medium heat, then add the diced red onion and bell pepper, sautéing until they are tender and fragrant.
Add the chicken to the skillet along with the chili powder, cumin, sea salt, and black pepper, cooking until the chicken is browned and no longer pink.
In a small mixing bowl, whisk together the red enchilada sauce and Greek yogurt until the mixture is smooth and creamy.
Slice the corn tortillas into 1-inch wide strips.
Spread two tablespoons of the creamy sauce across the bottom of the prepared baking dish.
Place half of the tortilla strips over the sauce, followed by the chicken and vegetable mixture, and half of the remaining sauce.
Layer the remaining tortilla strips and the rest of the sauce on top, then finish by sprinkling the sharp cheddar cheese evenly over the surface.
Bake for 15 to 20 minutes until the sauce is bubbling at the edges and the cheese has melted into a beautiful golden crust.