Preheat oven to 350°F (175°C).

In a large skillet, brown ground beef over medium-high heat.

Add chopped onion and bell pepper to the skillet and cook until softened.

Drain any excess grease from the skillet.

Stir in taco seasoning according to package directions.

In a baking dish, create a base layer with half of the crushed Doritos.

In a large bowl, combine the seasoned ground beef mixture, cream of mushroom soup, and nacho cheese.

Mix well to ensure all ingredients are evenly combined.

Pour the beef mixture over the Doritos base in the baking dish.

Top the beef mixture with the remaining crushed Doritos.

Sprinkle shredded cheddar cheese evenly over the top.

Bake in the preheated oven for 10 minutes, or until the cheese is melted and bubbly.

Let cool slightly before serving.

Garnish with sour cream or salsa, if desired.