The neighborhood around Sultanahmet and the Grand Bazaar introduces an interesting plot twist into the slow-cooked Choose Your Own Adventure that is the esnaf lokantası experience. As described on this website, an esnaf lokantası is the Turkish workingman’s lunch spot, to be found in every hard-working neighborhood, nationwide.
Despite being the city’s touristic ground zero and a neighborhood not often associated with much of anything authentic, I am here to insist: Sultanahmet IS still an esnaf (workingman’s) sort of place. There are hordes of starving tourists, to be sure, but there are just as many hungry shop guys, carpet-menders, hotel managers, printers, bookbinders, lawyers, cops, dentists and diverse and assorted clerical types – all of whom, occasionally, cannot face another tost or döner sandwich, and need a real lokanta lunch. At the same time, Turkish men are oftentimes as finicky as Goldilocks when it comes to the lokanta’s slow-cooked food: if a dish is too oily or too watery, too spicy or too bland, too runny or too lumpy, the waiter will hear about it, as will everyone at the table. The true esnaf will not just eat lokanta fare at any old place.
So, where do the workingmen of Sultanahmet all go? Below are two options:
The Major Guide Books tend to focus on Havuzlu and Bahar – perfectly decent spots right inside or close to the Grand Bazaar. And on any given day, each of these places will have a few clutches of lunching locals. But I suggest that you leave these places to the modern-day Baedeker set. Head for Sefa instead.
At Sefa, there are no dishes offered up to appease a tourist sensibility. Ergo, every dish is made as (or perhaps, ahem, better than) every Turkish mother would make it, and everything is delicious – choose according to your own taste, confident that whatever you choose, it will rock. For example: last visit, a stewed celeriac dish altered my worldview. Sefa is bustling all day, every day – but do not be intimidated by the ranks of be-suited locals hunched over the plates, cleaning them up with single-minded devotion. Traffic moves swiftly and efficiently through Sefa (another sign of its esnaf cred). So head on in, belly up to the glass display case in back and feed your inner workingman.
Some tips: do not be shy about putting together a karışık (mixed) plate, with small bits of a number of things, or ordering a few az (just-a-little) portions to share. Variety is the spice of life, so try as many dishes as you want!
Address: Nuruosmaniye Caddesi 11A, Cağaloğlu
Web: www.sefarestaurant.com.tr 
Hours: Open for lunch only; get there early (before 1pm) for better selection.
The Ottoman Archives* were, for years, located smack in the middle of Sultanahmet and, as such, generations of starving students of Ottoman history (as well as various others) faced the challenge of finding a cheap and reliable lunch spot in close proximity to the archives. Akdeniz was that place for decades.
I first learned of Akdeniz through a friend who often needs a bowl of lentil soup before facing the Grand Bazaar and, when in need, heads there. Recently, though, an Ottoman historian friend and I stopped by for lunch – a bit of a nostalgic indulgence: my friend used to have lunch at Akdeniz every day, when camped out in the Archives in the 1980s. Turns out, they still do many things well (they also run an excellent pide operation next door: Karadeniz). The slow-cooking side of things might not offer up the daily smorgasbord of elaborate options that one finds at Sefa, but Akdeniz does offer five or six dishes, all simple, very well made and cheap – ideal for a quick, unfussy lunch (an overflowing mixed plate is usually around 10 TL). And unlike most places in the neighborhood, at Akdeniz there are no smirking young bucks, no jaded, shifty glances and, as far as I can tell, minimal English spoken.
Both Akdeniz and Karadeniz are located on one of the many pedestrian side streets off Divan Yolu, right at the Sultanahmet tram stop. Once you make it there, you can sit at any of the shady outdoor tables and relax – the staff does not tolerate unsolicited chit-chat with their guests, so no one will pester you (and if someone does, the cashier will run them off, if you throw him a help-me look). If you want pide, you can always sit at either establishment and order from both, if you wish.
*Yes, yes, I know. One archive of many. I refer to the Başbakanlık Archives.
Address: Hacı Tahsinbey Sokak, Sultanahmet
Web: www.karadenizpide.net