Preheat your oven to 375°F (190°C) and lightly grease a small oven-safe baking dish.
Heat the olive oil in a skillet over medium heat, then sauté the diced yellow onion and red bell pepper until they are soft and fragrant.
In a medium mixing bowl, combine the cooked shredded chicken breast, Greek yogurt, 0.25 cup of the enchilada sauce, sautéed vegetables, sea salt, black pepper, and garlic powder.
Slice the corn tortillas into 1-inch wide strips.
Spread a thin layer of the remaining enchilada sauce on the bottom of the baking dish, then layer half of the tortilla strips.
Spread the creamy chicken mixture over the tortillas, then top with the remaining tortilla strips and the rest of the enchilada sauce.
Sprinkle the shredded sharp cheddar cheese evenly over the top.
Bake for 15 to 20 minutes until the sauce is bubbling and the cheese has melted into a golden crust.
Remove from the oven and garnish with chopped fresh cilantro before serving warm.