Preheat the oven to 375°F (190°C) and lightly grease a 9x13 inch baking dish.
In a large skillet over medium-high heat, cook the ground beef and diced onion until the beef is thoroughly browned. Drain any excess fat.
Add the taco seasoning and water to the beef mixture. Simmer for 5 minutes until the sauce has thickened, then remove from heat.
Spread half of the tortilla chips in an even layer at the bottom of the prepared baking dish.
Layer half of the seasoned beef mixture, half of the black beans, half of the corn, and 1.5 cups of the shredded cheese over the chips.
Repeat the layers with the remaining chips, beef mixture, beans, and corn. Top with the remaining 1.5 cups of shredded cheese.
Bake for 15 to 20 minutes, or until the cheese is melted and the edges are bubbling.
Remove from the oven and top with salsa, pickled jalapeños, sliced green onions, and dollops of sour cream before serving.