Heat the oven to 350 °F and set a rack in the center position. The casserole bakes more evenly in the middle of the oven, and the cheese melts without overbrowning too fast.

Warm the olive oil in a skillet, add the ground beef, and cook over medium-high heat for 5 minutes while breaking it into small pieces. You want steady sizzling and some browned edges on the meat before moving on.

Add the chopped onion, chili powder, garlic powder, and cumin, then cook for 5 minutes more. The onion should soften and the spices should smell fragrant and toasty, which means they have bloomed in the hot fat.

Spread the crushed Doritos evenly across the bottom of a 9x13 baking dish. An even layer helps the base support the filling instead of collapsing into wet pockets.

Spoon off most of the excess fat from the skillet if needed, then stir in the black beans, corn, salsa, and half the cheese until warmed through. The mixture should look thick and scoopable, and the cheese should disappear into the filling as it melts.

Spoon the beef mixture evenly over the Doritos. Gentle, even spreading keeps the chip layer in place and helps every serving hold together.

Scatter the remaining cheese over the top and bake uncovered for 15 to 20 minutes while you prep any toppings. The casserole is ready when the cheese is fully melted and the edges are bubbling.

Let the casserole sit briefly, then serve it plain or finish with your favorite toppings. A short rest helps the layers settle so you get cleaner portions instead of a loose scoop.