Preheat your oven to 350°F (175°C). Grease a 9 x 13-inch casserole dish.

Brown the lean minced beef and onions together in a large skillet over medium heat for about 5-7 minutes. Drain any excess fat.

Combine taco seasoning, chili powder, and water into the meat mixture, stirring well. Bring to a gentle boil, then reduce heat and let simmer for 3-5 minutes.

Stir in diced tomatoes, tomato sauce, corn, and kidney beans. Allow to simmer for another 5 minutes.

Layer 4 cups of corn chips at the bottom of the greased dish. Sprinkle 1 cup of cheese on top.

Spread the beef mixture evenly over the chips and cheese, then top with the remaining cheese.

Bake for 18 to 20 minutes, until the cheese is melted and bubbly.

Garnish with remaining corn chips and toppings like diced tomatoes, sour cream, green onions, or avocado before serving.