Prepare the Dish: Preheat oven to 400°F. Lightly mist a 9×13-inch baking dish with cooking spray and set aside.

Cook the Sausage: In a large skillet over medium-high heat, cook sausage until browned, crumbling as it cooks. Transfer to a plate, leaving a tablespoon of grease in the pan. Add oil if none remains.

Sauté Vegetables: Add onion and bell pepper to the skillet. Cook for 5 minutes, stirring occasionally, until softened. Add garlic and cook 1–2 minutes more until fragrant.

Mix the Filling: Stir in salsa, beans, corn, cumin, salt, and cooked sausage. Combine well, then remove skillet from heat.

Prepare the Eggs: In a separate bowl, whisk together eggs and milk until smooth. Set aside for layering.

Layer the Casserole: Arrange half the tortillas in the bottom of the baking dish. Top with half the sausage mixture, half the egg mixture, and half the cheese. Repeat with another layer of tortillas, sausage filling, egg mixture, and cheese.

Bake to Perfection: Cover dish with foil and bake for 45–50 minutes until the center is set and no longer jiggly. A toothpick inserted in the center should come out clean.

Cool and Serve: Transfer the dish to a wire rack. Let cool for 10 minutes before sprinkling with toppings. Slice and serve warm.