Cook ground beef, onion, and garlic in a skillet until browned and softened.
Add taco seasoning and water; simmer 2 to 3 minutes until slightly thickened.
Stir in salsa, black beans, and corn; cook briefly, then let rest to thicken.
Preheat the oven to 375°F and spread a thin layer of the meat mixture in the baking dish.
Layer tortillas, meat mixture, and cheese repeatedly, finishing with a generous cheese layer.
Bake 20 to 25 minutes until the cheese is melted, bubbly, and lightly golden.
Let rest 5 to 10 minutes before slicing; serve with sour cream, guacamole, salsa, or lettuce.