Bengisu K.
Yelp
As a Turkish person I must admit that rating the food here is a bit tough but I'm doing it per what goes and is available in North America, rather than a restaurant in proper Turkey.
Stuffed vine leaves, a staple of feasts at home in Turkey, is rarely done well in restaurants, especially in North America. Avesta gets it right most of the time, which is a blessing; if you are not vegetarian, I highly recommend ones with minced meat over veggie ones as the latter are harder to make well and Avesta does screw it sometimes too but their minced meat ones are almost always very good and definitely worth ordering.
Their mezze (appetizer) options are all very good; the way they make tzaziki/cacik is more to the Greek style than authentic Turkish but it fits well with rest of their menu. Be sure to try their gozleme, which are savoury stuffed flat bread buns (or 'crepes', one could say); they prepare those fresh and right in front of you at the store on a traditional saj stove. Similarly, their manti (tiny dumplings served in lovely Turkish yoghurt with mint-tomato paste sauce) is very good; I know that they work with local Turkish women to prepare those and hence am not surprised at the quality. Sometimes I find the filling to be a bit too much, but that's just my not-super-into meat self.
Their saj kavurma (sauteed chunks meat in special traditional pan) are all very delicious and also very hot/spicy; if you are not good with pepper, tell them in advance ordering this. I'd say this is their most authentic food out of all the entrees. I like their Inegol kofte (a kind of Turkish meatballs closely related to Balkan-style meatballs) and Beyti kebab (minced meat kebab wrapped in very thin flat bread, cut with sauce drizzled over), neither is anything like the original. Most of their entrees are in fact not exactly 'authentic' but they are tasty copies; the sort of food mums will make at home in Turkey as knock-offs of fancy restaurant kebabs that are very hard to make. It will give you a good idea of the sort of herbs and spices used in Turkish cuisine as well as the tones of taste and variety, even if they are not exactly authentic.
Their desserts are very meh; even by home-made standards, very very meh so I'd say skip it. Tea is alright; your regular Turkish tea; honestly not worth the cost, but hey if you have never had it, it's authentic Turkish tea so you may give it a try.
All in all: this place is a good place to go just for the bread and appetizers to be honest. In fact sometimes I go just for that. Also: do not expect quality waiting staff or service. They are polite and nice but also slow and often short in numbers. Turkish food itself takes very long to make, hence even Turkish people like me coming to a restaurant when we crave borek or kofte, so if you aren't willing to wait fifteen or thirty minutes for your food, don't bother--go to McDonalds; this is not 'fast food'. In Turkey its food probably wouldn't even be regarded as 'decent' by our restaurant standards, but it is very decent by North America standards.