It is difficult to find a non-kosher restaurant in Jerusalem's Jewish neighborhoods. In Tel Aviv, the situation is different. There it is often difficult to find a kosher restaurant. During my current working-hours-exile in Tel Aviv I met a Belz Hassid near their Cheder on Ahad Ha'am Street, and I asked him if he knew of a strictly kosher restaurant in the area. He told me that at the end of Mazeh Street near the intersection with Allenby Street there is a restaurant called "Yeshurun" owned by a Chabbadnik, and that he himself eats there. I stored that information in my brain for later retrieval.
A few days later I went to the restaurant. There are certain places in Israel that entering them is like entering a time warp. "Yeshurun" is one of them. The cuisine is stictly Eastern European. You will find all the classic "Jewish" food that your grandmother (if she was Ashkenazic) cooked: Gefilte Fish, Kasha, Cholent, Knishes, Latkes, etc. The owner of the restaurant, Zusha, can be heard chatting with his workers not only in Hebrew but also in Russian and Yiddish. This is probably as close to being in a shtetl as you can get in downtown Tel Aviv.
Zusha is a Lubavitcher Hassid, and he runs his business like one. Children that learn in a nearby school stop by after school hours to receive a free treat from Zusha. Sometimes it's a candy, sometimes it's a soft drink. The day I was there, Zusha was handing out doughnuts.
Did I say the treat was free? Well, it's almost free. If you want a treat from Zusha you have to say the verse, "Here O Israel, the Lord is our God, the Lord is one." And of course the proper blessing must be recited over the treat in question. (This is reminiscent of the Midrash where the patriarch Abraham teaches his guests to thank God for the food that he served them.) The kids don't seem to mind paying the price.
By the way, the food is pretty good.