Brown ground beef in a large skillet and drain off any excess fat.

Add the taco seasoning and 2 cups of water to the browned ground beef.

Bring the mixture to a boil, then reduce heat to low.

Simmer for 15 minutes, allowing the sauce to thicken.

Preheat oven to 350°F (175°C).

In a 13 x 9-inch casserole dish, create the first layer with crushed Doritos.

Top the Doritos with chopped onions and green pepper.

Pour half of the meat sauce mixture over the vegetables.

Arrange half of the sliced Velveeta cheese on top of the meat sauce.

Repeat the layers: crushed Doritos, onions, green pepper, remaining meat sauce, and the remaining sliced Velveeta cheese.

Cover the casserole dish with foil.

Bake in the preheated oven for 30 minutes, or until heated through and the cheese is melted and bubbly.