Aptly Named Tenderloins

• Tenderloin fillet comes from the middle of the cow's back, where the muscles have little work to do and remain very tender. Also called filet mignon from the piece of tenderloin at the very end of the fillet or Chateaubriand from a 19th century French recipe, tenderloin fillets have no bones attached to them so have less beefy taste than steaks with bones. The same tenderloin cuts with bones left in are called porterhouse and T-bone steaks.

Moving to the Rear

• Top sirloin appears behind the tenderloin, but in front of the bottom sirloin, sirloin tip and rump sections -- it's a continuation of the tenderloin muscle. Less tender than tenderloin fillet, top sirloin is also less expensive as well but has slightly more beef flavor than tenderloin fillet. Less common than top sirloin, bone-in cuts of sirloin appear in your butcher counter as pinbone, flat bone, round one and wedge steaks.

Into the Fire

• Both top sirloin and tenderloin fillet steaks are tender enough to cook on the grill, under the broiler or in a skillet. In all cases, let the steaks warm to room temperature for about 30 minutes before cooking, sear the steaks over high heat until they get a crusty, brown coating and reach 145 degrees Fahrenheit, for medium rare, on an instant-read meat thermometer. Equally important, let the steaks rest for three to five minutes before serving so the juices get reabsorbed into the muscles.

Sauces for Soaking and Pouring

• Tenderloin fillets don't need to marinate because they are already so tender, but they benefit from flavorful sauces used after cooking. Possibilities include herbed butter, garlicky chimichurri with parsley, spices and vinegar, or a rich brown sauce with tomato puree and sauteed mushrooms. Marinate less tender top sirloin for six to 24 hours in the refrigerator with a marinade using your favorite vinaigrette, steak sauce with garlic or an Asian marinade with soy sauce, garlic and ginger.