Beef tenderloin is a short section of muscle that runs from under the cow’s inner rib to its rear end. Because this region of muscle gets minimal exercise, tenderloin meat is extremely tender and naturally moist. Not surprisingly, the sumptuous tenderloin is the source of expensive beef cuts such as filet mignon. Purchasing an entire tenderloin and slicing the filets yourself doesn’t require advanced butchering skills, but you should follow certain guidelines to optimize the tenderness of your tenderloin filet.