Preheat the oven to 350°F.
In a large skillet, heat oil over medium heat. Add in the onions and cook for 5 minutes. Add in the garlic and the ground beef and cook until the meat is no longer pink, breaking up the clumps with a wooden spoon.
Add in the taco seasoning, Ro-tel, and salsa. Cook for 5 minutes, stirring occasionally.
Stir in the sour cream evenly and then remove the mixture from the heat.
Pour half of the meat mixture into the bottom of a 9×13 pan. Top with 1 cup of the cheese and half of the Doritos. Repeat the process with the remaining ingredients, topping with the remaining cheese.
Cover the pan with foil and bake for 20 minutes.
Remove the foil and bake for 10 more minutes.
Garnish as desired and serve warm.