This is what you need:
Put a couple of tablespoons of olive oil in the pan and cook the turkey and onion. Then add 1 small can enchilada sauce and let simmer for 10-30 minutes, the longer the better because the seasoning can infuse the turkey. Using the large can of sauce, pour a thin layer of sauce on the bottom of a large casserole dish. Warm the tortillas in microwave and then fill with meat mixture and make one layer of enchiladas in the dish. (I can fit 12 in mine.) Then pour the large can of sauce over the enchiladas, top with cheese, and heat in the microwave until the enchiladas are nice & hot and the cheese is completely melted.