Matambre is the name of a very thin cut of beef in Argentina, Uruguay and also Paraguay. It is a rose colored muscle taken between the skin and the ribs of the steer, a sort of flank steak. It is not the cut known normally in the U.S. as flank steak. Some people refer to it as the 'fly shaker', because it is the muscle used by the animal to twitch to repel flies and other flying insects. Matambre is cut from the side of the cow, between the skin and the ribs. The scientific name for the muscle is cutaneous trunci. It is a thin rose colored muscle, also known in packing houses as 'fly shaker' or 'elephant ear'. It is also known as the 'twitch' muscle because the animal makes it twitch or tremble to repel flying insects like flies. It is very thin and lends itself for rolling up with different stuffings. (Source: Wikipedia.org, CC BY-SA)