Sauce : Heat the oil in a 12 inch skillet over medium heat. Add the onion and salt and cook until softened, about 5 minutes.
Stir in the chili powder, garlic, cumin and sugar. Cook 15 seconds. Stir in the tomato sauce and water.
Bring to a simmer and cook until slightly thickened, about 5 minutes. Season to taste with salt & pepper; reserve.
Enchiladas : Adjust the oven rack to the middle position. Heat oven to 400 F.
Combine the turkey, 2-cups, cheddar, ½-cup of sauce, chilies and cilantro. Season with salt & pepper to taste. Stack the tortillas on a microwave safe plate.
Cover with plastic wrap and microwave on high until warm, about 40-60 seconds. Lightly coat a 9x13 inch baking dish with vegetable spray.
Spread the warm tortillas out on a clean counter top. Place ⅓-cup of the turkey mixture evenly down the center of each tortilla. Tightly roll the tortilla and then lay seam side down in the baking dish.
A second layer will be necessary. Lightly spray the enchiladas with vegetable spray.
Pour 1-cup of the remaining sauce over the enchiladas to coat thoroughly. Sprinkle with remaining cheddar cheese down the center of the enchiladas.
Cover the dish with foil and bake 20-25 minutes, until heated through. Remove foil and continue to bake until cheddar cheese browns, about 5 minutes.