Preheat and prep: Heat your oven to 375°F (190°C).
Lightly grease a 9x13-inch baking dish.
Brown the meat: In a large skillet over medium-high heat, cook the ground beef, breaking it up with a spoon, until browned and no longer pink, 5–7 minutes. Drain excess fat if needed.
Sauté aromatics: Add the onion and cook until softened, about 3 minutes. Stir in the garlic and cook 30 seconds until fragrant.
Season and simmer: Sprinkle in taco seasoning, then add salsa, black beans, diced tomatoes with green chiles, corn, and water.
Stir and simmer 3–5 minutes, until slightly thickened. Taste and season with salt and pepper.
Layer the base: Spread half the crushed tortilla chips in the baking dish. Spoon half the meat mixture over the chips.
Top with one-third of the cheese.
Repeat: Add the remaining chips, spread the remaining meat mixture on top, and finish with the rest of the cheese.
Bake: Place the casserole in the oven and bake 15–18 minutes, until the cheese is melted and bubbly around the edges.
Rest and finish: Let it rest 5 minutes so it sets. Sprinkle with cilantro if using.
Serve with toppings: Add shredded lettuce, tomatoes, green onions, sour cream, jalapeños, avocado, and a squeeze of lime. Serve hot with extra hot sauce on the side.