Beef tenerloin, or eye fillet (New Zealand and Australia), is cut from the loin of a steer or heifer. As with all quadrupeds, the tenderloin refers to the Psoas major muscle along the central spine portion, which more or less hangs between the shoulder blade and hip socket. This muscle tissue does very little work, so it is the most tender part of the cow. The tenderloin can either be cut for roasts or for steaks.