Add ground beef, onions and garlic to a large deep skillet over medium heat. Cook for 5 to 7 minutes
Stir in taco seasoning, ROTEL diced tomatoes with green chilies, salsa, diced chilies and sour cream.
Heat for 1 to 2 minutes, until mixture heats through.
Spread 1/3 of Doritos on the bottom of the prepared casserole dish.
Top with half the beef mixture.
Add another 1/3 of Doritos on top.
Add remaining beef mixture on top of that.
Add the last 1/3 of Doritos on top.
Sprinkle with cheddar and Monterey Jack cheese.
Cover with aluminum foil and bake for 20 minutes at 350F.
Remove foil and bake for another 10 minutes. Serve hot.