The Cook's Thesaurus names beef loin, especially filet mignon, as the tenderest cut of beef but not necessarily the most flavorful. Cooking beef in foil adds flavor while preserving the natural texture of the meat. Foil contains the beefy, rich juices to make serving and cleanup a breeze. You can cook beef in foil virtually anywhere you have a heat source. Learn to oven-bake tender beef wrapped in foil before experimenting with cooking it in your barbecue or buried in hot coals.
Remove the meat from your refrigerator about a half an hour before cooking to allow the exterior of the beef to come to room temperature. Place the meat in a shallow dish and cover it with plastic wrap to keep it clean. Cold beef tends to burn on the outside and grow tough on the inside when suddenly introduced to heat.
Preheat your oven to 300 degrees Fahrenheit. Verify the temperature with a thermometer placed in the center of your oven. Allow your oven heat to stabilize to ensure even cooking.
Pour the dry-onion soup into a bowl. Stir in just enough water to make a thick paste.
Tear off a sheet of aluminum foil large enough to liberally wrap the meat. Put the foil on a baking sheet or in a wide casserole to make transporting the cut of meat in and out of the oven safer. Place the meat in the center of the foil.
Dry the meat with a paper towel or clean kitchen towel. Slice into any large areas of fat with a knife but do not remove the fat. The slices allow the meat and fat to shrink at different rates without curling. Apply salt and pepper to the meat. Strike the beef with a meat tenderizer to make the meat tenderer and to drive the spices into the meat.
Smear the onion-soup paste evenly on all sides of the meat. Add leftover onion-soup paste around the sides of the meat. Wrap the meat in the foil, sealing the foil completely.
Put the dish in the oven. Bake it for three-and-a-half to four hours. Check the meat with a thermometer. Remove the meat when the internal temperature reaches 145 degrees Fahrenheit. Allow the meat to rest for three minutes before serving it. The beef will remain the same temperature or even grow warmer during this rest period, killing potentially harmful bacteria, according to the Food Safety Inspection Service.