Preheat your oven to 375°F (190°C).
Dice the chicken breast into small, uniform bite-sized pieces.
Heat the olive oil in a skillet over medium heat and sauté the chicken with sea salt, black pepper, and cumin until the chicken is browned and cooked through.
Add the diced red onion and bell pepper to the skillet, cooking for 3-4 minutes until the vegetables are tender-crisp.
In a small mixing bowl, whisk together the red enchilada sauce and plain Greek yogurt until you have a smooth, creamy sauce.
Slice the corn tortillas into 1-inch wide strips.
Spread a small spoonful of the creamy sauce at the bottom of a small oven-safe baking dish to prevent sticking.
Layer half of the tortilla strips on the bottom, followed by half of the chicken and vegetable mixture, and half of the remaining sauce.
Repeat the layers once more with the remaining tortillas, chicken, and sauce.
Sprinkle the shredded sharp cheddar cheese evenly over the top of the final layer.
Bake for 15-20 minutes, or until the sauce is bubbling at the edges and the cheese has melted into a golden crust.
Remove from the oven and garnish with freshly chopped cilantro before serving warm.