Trippa alla Fiorentina
Trippa alla Fiorentina is Florentine-style tripe -- which is served hot in a tomato sauce, with parmesan. You can get it in restaurants, and people do of course make it at home, but mostly typically you get it from tripe vendors, who set up their food carts at various places in the city, particularly in the central market and in the Cascine park.
The tomato sauce is generally made from tomato, onion, carrot, and celery. Some vendors versions don't add celery and carrot; they might use parsley and white wine instead, and the amount of tomato in the sauce will vary from tripe vendor to tripe vendor. At some vendors such as Nerbone, the sauce is more of a dark broth, with a few pieces of simmered fresh tomato in it.
The vendors offer different types of tripes; some carts alternate what types of tripe dishes they sell on what day. None of the tripe sold has any of the, erm, aroma associated with tripe elsewhere in the world. The tripe vendors source their tripe thoroughly prepared and partially cooked from special tripe butchers, who simmer the tripe for about 75 minutes in a broth of celery, onion, carrot, tomato and herbs. The vendors finish off cooking it at their carts, simmering it for another 20 minutes in a similar broth.
You can ask for your tripe in buns called "panini", or as part of a tripe salad, or straight up, on a plate. If you get it on a bun, you can ask for the bun to be dipped in the simmering tripe broth. However you get it, garnishes such as green sauce ("salsa verde"), salsa piccante (a chile oil), parmesan, etc, are available.
Perhaps the most favoured type of tripe in Florence is that called "lampredotto" ("reed tripe" in English), the lining of the fourth stomach. "Lampredotto" is more likely to be served with a green sauce; the other three types of tripe are morely likely to be in a tomato sauce with parmesan.
There are always line-ups at the tripe carts. The carts are open from about 8:30 am to 7:30 pm, except on Sundays; some close earlier in the day; some close Saturdays as well. Many don't operate during August, the high tourist season. Some will have a few trestle tables around them to sit and eat.
You can also get Florentine trip at restaurants, where it might be served with boiled potatoes, or cannellini beans and olive oil.