Preheat your oven to 350°F (175°C).
In a large skillet over medium heat, cook the ground beef and diced onion until the beef is browned and the onion is translucent, about 5-7 minutes. Drain any excess fat.
Stir in the taco seasoning, black beans, corn, and salsa. Cook for an additional 3-4 minutes until heated through.
In a 9x13 inch baking dish, layer half of the crushed tortilla chips on the bottom.
Spread the beef mixture evenly over the tortilla chips.
Sprinkle 1 cup of shredded cheddar cheese over the beef mixture.
Add the remaining crushed tortilla chips on top, followed by the remaining cheese.
Bake in the preheated oven for 20-25 minutes, or until the cheese is melted and bubbly.
Remove from the oven and let it cool for 5 minutes. Top with sour cream, green onions, and cilantro if desired before serving.