In a large skillet, brown ground turkey. Add onions and corn, cooking until the onions are tender.
Add taco seasoning, and water - mix until well combined. Remove from heat mix in sour cream and salsa.
Using a 2 quart baking dish, layer a few handfuls of Doritos, slightly crushed, to the bottom. Spoon half of the meat mixture over the top, sprinkle with half of the cheese. Repeat with the remaining ingredients.
Bake for 20 minutes until heated through and cheese is melted.