Known as the holiest of holies of Italian cuisine, the Florentine-style beef steak is prepared exclusively with dry-aged beef from the Chianina cattle, which is particularly prized for its tenderness. Even though bistecca alla Fiorentina is often described as a T-bone steak, it is much closer to a porterhouse - since it's cut closer to the center, the tenderloin is much larger than the one on a regular T-bone.
Also, bistecca alla Fiorentina must be thick; the cut needs to be at least three fingers wide so that when the meat is grilled over a very hot flame, a nice, slightly charred crust forms on the outside of the steak while the inside remains succulent.