Preheat the oven. Set to 375°F (190°C). Lightly grease a 9x13-inch baking dish with cooking spray or oil.
Make the high-protein sauce. In a bowl, whisk enchilada sauce with Greek yogurt until smooth.
Stir in cumin, chili powder, garlic powder, and a pinch of salt and pepper. The sauce should be creamy and pourable.
Prep the filling. In a large bowl, combine shredded chicken, black beans, corn, diced green chiles, red onion, and bell pepper. Season lightly with salt and pepper.
Toss with 1/2 cup of the sauce to moisten.
Soften the tortillas. Stack and wrap in a damp paper towel. Microwave for 30–45 seconds so they’re pliable and less likely to tear.
Layer one: Spread 1/2 cup of sauce on the bottom of the baking dish. Add a layer of tortillas, tearing as needed to cover the base.
Layer two: Spoon half the chicken mixture over the tortillas.
Drizzle with more sauce. Sprinkle with 2/3 cup cheese.
Repeat: Add another layer of tortillas, the remaining chicken mixture, more sauce, and another 2/3 cup cheese.
Top layer: Finish with a final layer of tortillas, the remaining sauce, and the rest of the cheese. Press gently to settle.
Bake. Cover with foil and bake for 20 minutes.
Remove foil and bake another 10–15 minutes, until the cheese is melted and lightly browned and the edges bubble.
Rest and garnish. Let it sit 10 minutes to set. Top with chopped cilantro and a squeeze of lime. Add avocado slices if you want extra richness.
Serve. Cut into squares and serve warm with a simple side salad or steamed vegetables.