there are quite many of them 🙂 difficult to make a list.
For great restaurants in Florence, take a look here, for Siena here.
Some of my favorite restaurants across Tuscany are:
–Osteria Baccus in Pienza
–Osteria Passignano in Chianti
–Gli Orti di via Elisa in Lucca
–Osteria del Conte in Montepulciano
If you have a particular place in mind let me know so I can give more suggestions,
Have a nice weekend,