Prep the oven and pan: Heat oven to 375°F (190°C). Grease a 9x13-inch baking dish with a little oil or cooking spray.
Sauté the veggies: Warm olive oil in a skillet over medium heat.
Add onion, bell pepper, and jalapeño. Cook 4–5 minutes until softened. Season with a pinch of salt and pepper.
Mix the filling: In a large bowl, combine shredded chicken, sautéed veggies, black beans, corn, salsa (reserve 1/2 cup for the top), chili powder, cumin, smoked paprika, and garlic powder.
Taste and adjust salt.
Layer the tortillas: Place a layer of tortillas on the bottom of the baking dish, tearing pieces to cover edges. Aim for full coverage.
Add filling and cheese: Spread one-third of the chicken mixture over the tortillas. Sprinkle with about one cup of cheese.
Repeat layers: Add another tortilla layer, another third of the filling, and more cheese.
Repeat once more for three total layers.
Top it off: Spread the reserved 1/2 cup salsa over the top layer and finish with the remaining cheese. Press down gently to compact the layers.
Bake: Cover with foil and bake 15 minutes. Remove foil and bake another 10–12 minutes until the cheese is melted and the edges are lightly browned.
Rest and garnish: Let the casserole rest 10 minutes so it sets.
Top with cilantro, green onions, and a squeeze of lime. Serve with sour cream or Greek yogurt.