If we stand back and think about this, all the restaurants are in Turkey and all the Chefs are Turkish. So the food is authentic. The only reason people ask for authentic Turkish Food is because the holiday makes want British, Italian, Chinese, Indian type food.. i.e. Full English Breakfasts, Sunday Roasts, Curries, Pizzas and of course Steak.. the one food that is always first to be mentioned when a local restaurant is recommended.
All the local restaurants have Turkish Menus and serve Turkish food, we just have to ask for it.
I would also add that the little cafe next to the Delta where all the taxi drivers eat have really good "Turkish Food" when my son and daughter in law where on their honeymoon last year staying in the Delta. They got hungry and my son went out late at night to find some food he and my d.i.l. raved about the food they got there which was meat balls and kebaps. In fact, they kept returning to the place. I don't recall ever seeing a recommendation for this cafe and don't know it's name, but I always see locals eating there.
