....it seems as if Istanbul has a number of GF places now.
Below are just a few websites to check out: Got the following review from TripAdvisor
The owner of this restaurant (Buhara 93) Ibrahim Sonmez will cater for celiacs and others who can not eat gluten. He arranged for me to have a chicken dish with rice and salad that was very tasty. He is also a lovely man who speaks great English. He is open for early breakfast through to late dinners. He can be contacted on info@buhararestaurant.com he also has some beautifully renovated brand new classy rooms for rent