Preheat oven to 400°F (204ºC) and spray a 9×13-inch baking dish with cooking spray.

In a large skillet over medium heat, cook ground beef and chopped onion until no longer pink. Drain excess fat.

Stir in taco seasoning, drained diced tomatoes, diced green chilies, sour cream, and cream of mushroom soup until heated through.

In the prepared baking dish, layer one-third of crushed Doritos at the bottom, then half of the beef mixture. Repeat with another third of Doritos and remaining beef mixture. Top with the last third of Doritos and sprinkle shredded Jack and cheddar cheese evenly on top.

Bake uncovered for about 20 minutes until heated through and cheese is bubbly.