Pittsburgh rare is a term describing a degree of doneness for beef steaks.
It is considered to be an internal temperature of 110 F (43 C.) The steak should be very charred on the outside, even having black bits on it, but very rare (as in blood red) and still quite cold on the inside. It is usually done with steaks cut at least 1 1/2 inches (4 cm) thick, particularly Porterhouse or strip steaks, but the method can also be applied to a steak au poivre.
It is best achieved with lots of flames to overcook the outside quickly without heating the inside. It can be approximated by searing in a cast-iron frying pan that has been heated to very hot before putting the steak in.
Popular mythology attributes this style of cooking a steak to steelworkers in Pittsburgh, Pennsylvania (who could presumably afford steak all the time for work, following the logic of this story), who would bring the steak to work with them uncooked, and at lunchtime, slap their steak onto the incredible (and no doubt dirty) surfaces of smelting furnaces. Other writers speculate that the method originated with a steak served to an out-of-town restaurant guest at the The Colony Restaurant (opened 1958 by Dean Steliotes) in Pittsburgh that was charred by accident; the cook explained it away saying that that was “Pittsburgh style”. The Colony restaurant in fact claims the story is true, though neither the cook, the customer or the year are named.
Sometimes it is called “Pittsburgh style”; sometimes in Pittsburgh itself it is referred to as “black and blue.”