Prep the oven and pan. Heat the oven to 375°F (190°C).
Lightly grease a 9x13-inch baking dish.
Sauté aromatics. In a large skillet over medium heat, warm the olive oil. Add onion and a pinch of salt. Cook 4–5 minutes until softened.
Stir in garlic and cook 30 seconds until fragrant.
Brown the turkey. Add ground turkey, breaking it up with a spatula. Season with salt, pepper, chili powder, cumin, and smoked paprika. Cook 5–7 minutes until no longer pink.
Add mix-ins. Stir in green chiles, black beans, and corn.
Pour in 1/2 cup enchilada sauce to moisten the mixture. Taste and adjust seasoning.
Layer the casserole. Spread 1/2 cup enchilada sauce on the bottom of the baking dish. Add a layer of corn tortillas to cover.
Spoon half the turkey mixture over the tortillas, sprinkle with 3/4–1 cup cheese, and drizzle with another 1/2 cup sauce.
Repeat. Add another layer of tortillas, the remaining turkey mixture, 3/4–1 cup cheese, and 1/2 cup sauce. Finish with a final layer of tortillas, the remaining sauce, and the remaining cheese on top.
Bake. Cover loosely with foil and bake 15 minutes. Uncover and bake another 10–15 minutes, until the cheese is melted and the edges are bubbling.
Rest and garnish. Let the casserole rest 10 minutes to set.
Top with cilantro and avocado, and serve with lime wedges and a dollop of sour cream or Greek yogurt.