Preheat the oven to 400°F (200°C). Line a large rimmed baking sheet with parchment paper or foil.
Heat the olive oil in a skillet over medium heat. Add the diced onion and cook for 2–3 minutes until softened.
Add the ground beef and cook for 6–8 minutes, breaking it into small crumbles until fully browned and cooked through.
Drain excess grease if necessary. Stir in the taco seasoning and water, then simmer until the beef is evenly seasoned and most of the liquid has evaporated.
Drain and rinse the black beans. Prepare the diced tomatoes, sliced jalapeños, and fresh herbs.
Spread half of the tortilla chips across the baking sheet. Add half of the beef, black beans, cheddar, and Monterey Jack cheese.
Add the remaining chips, beef, beans, and cheese to create a second layer.
Bake for 5–8 minutes, until the cheese is melted and bubbly.
Remove from the oven and top with diced tomatoes, jalapeños, sour cream, and fresh cilantro or green onions.
Serve immediately with salsa, guacamole, and lime wedges if desired.
