- 20 minutes
- 90 minutes
- 4 to 6 servings
- In a large skillet, sauté the onions and garlic in the butter along with the salt, pepper, and basil. Sauté until the onions are caramelized, about 10 minutes.
- Using a knife, cut a long slit down the center of the beef tenderloin, not all the way through, stay about ½-inch from the bottom of the beef. Then “open” the beef like a book and flatten it out a bit.
- Lay the Swiss cheese over the surface of the meat and then place the onion mixture on top of the cheese. Fold the beef “book” back together and tie it tightly with cotton kitchen twine (tie in about 6 places to keep it nice and tight).
- Thoroughly season the outside of the beef with salt and pepper
- Place the beef in a large roasting pan and cook in a 425-degree oven for about an hour or until the internal temperature of the beef reaches 160 degrees Fahrenheit when tested with a meat thermometer. (This is for medium.)