Preheat oven to 425 degrees.
Add beef to stovetop skillet and cook on medium heat.
Dice white onion and add to beef.
Meanwhile, prepare any additional toppings desired while beef is cooking.
Once beef has cooked, drain, add Taco Seasoning, and 1/4 cup of water.
Continue to heat beef and taco seasoning on medium heat until water has reduced and beef is seasoned.
Layer bottom of 9×13 baking dish with Doritos.
Add seasoned beef on top of Doritos.
Add shredded cheese on top of beef.
Bake in oven for 5-8 minutes until cheese is melted.
Remove from oven, add tomatoes, and any additional desired toppings, and serve!