Preheat the oven to 350°F (175°C).

In a large skillet over medium heat, add the ground beef and diced onion. Cook until the meat is browned and the onions are translucent, about 5-7 minutes.

Sprinkle the taco seasoning over the beef mixture and stir in the salsa. Cook for another 2-3 minutes until everything is well combined.

In a large baking dish, start layering your ingredients. First, spread half of the crushed tortilla chips evenly across the bottom.

Spoon half of the beef mixture over the chips, followed by half of the black beans and corn. Sprinkle with 1 cup of shredded cheese.

Add another layer of crushed tortilla chips, followed by the remaining beef mixture, black beans, corn, and top with the remaining cheese.

Cover the baking dish with foil and bake in the preheated oven for 25 minutes. Remove the foil and bake for an additional 10-15 minutes or until the cheese is bubbly and slightly golden.

Once out of the oven, let the casserole sit for about 10 minutes to set. Top with sour cream, fresh cilantro, and jalapeños if desired. Serve warm and enjoy.