Baltimore pit beef is barbecue that refuses to be barbecue: there is no smoke and no low-and-slow. A lean beef round is cooked hot and fast over open charcoal until the outside is heavily charred and the inside is still rare, then sliced thin against the grain to order. That is the defining move. Where most American barbecue renders fat over hours, pit beef is a grilled roast treated like a deli cut, and the contrast between a black, bitter char and a cool, red, tender interior is the whole sandwich.
The craft is in the cut, the slicing, and the dressing. The round is a lean cut with little marbling, so the technique compensates for what the meat lacks: a hard sear builds the crust and the flavor that fat would otherwise provide, and the meat is pulled while the center is still rare because cooked through it would go to rope. It is shaved thin on a slicer the instant it is ordered, so a lean cut stays tender in a thin, pliable pile rather than toughening. The carrier is a kaiser roll, sturdy enough to hold a juicy load but soft and unobtrusive, and it is deliberately not the point. The two non-negotiable dressings are the structure of the flavor: a sharp horseradish or horseradish-spiked tiger sauce that cuts the char and the beef, and raw onion for a pungent, crunchy counter to a rich, fatty char on a lean meat.
The variations stay close to the charcoal and the slicer. The doneness is an argument, with traditionalists holding the center rare and others taking it further; the tiger sauce ranges from a mayonnaise-and-horseradish bind to a thinner, sharper cream; corned beef or turkey sometimes joins the round on a combination build. It sits at the edge of the American barbecue family, related to it by the pile of sliced beef and the soft roll but separated from it by the open-fire, fast, rare method, and those codified regional builds each deserve their own article rather than being crowded in here.