Small place in the San Frediano area with indoor and outdoor tables. The car parks in the surrounding area are almost all paid and require a bit of wandering given the area and the various restricted traffic zones so be patient.
There were two of us and we had a coke, a small draft beer and two beef burgers, one with classic potatoes and one with sweet potatoes, really delicious, the meat melted in the mouth, cooked well and of excellent quality, the bread was soft and above all it didn't break.
You can make up each burger however you want, they bring you a card and you choose from the bread, to the meat, to the sauces (bacon is €1 more, while other things depend, extras are €0.50 more).
They also offer vegan and gluten-free burgers.
Super recommended, too good, excellent quality/price, the only thing is the smell will stay with you a bit.