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Sliced French Onion Beef Tenderloin on a platter.
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French Onion Beef Tenderloin

French Onion Beef Tenderloin is tender, juicy beef topped with sweet caramelized onions and melted Gruyère cheese. With a rich onion sauce, it is a beautiful main dish for Thanksgiving, Christmas, or any special dinner!
Prep Time20 minutes
Cook Time1 hour
Total Time1 hour 20 minutes
Course: Dinner, Main Course
Keyword: French Onion Beef Tenderloin
Servings: 8 people
Calories: 484kcal
Author: Amanda Rettke--iamhomesteader.com

Ingredients

Beef Tenderloin

  • 1 whole (4 to 5 pounds) beef tenderloin, trimmed, tied
  • 1 tablespoon olive oil
  • 2 teaspoons kosher salt
  • 1 teaspoon freshly ground black pepper
  • 2 tablespoons unsalted butter, softened

French Onion Sauce

  • 3 tablespoons unsalted butter
  • 3 large yellow onions, thinly sliced (about 6 cups)
  • ½ teaspoon kosher salt
  • 1 teaspoon fresh thyme leaves
  • ½ cup (120 g) dry white wine
  • 1 ½ cups (360 g) beef broth
  • 1 tablespoon unsalted butter, cold
  • Kosher salt and freshly ground black pepper, to taste

For Finishing

  • ½ cup Gruyère cheese, finely shredded
  • Fresh thyme, optional, for garnish

Instructions

Prepare the Beef Tenderloin

  • Remove the beef tenderloin from the refrigerator about 30 minutes before cooking.
  • Preheat the oven to 425°F.
  • Pat the tenderloin thoroughly dry with paper towels.
  • If needed, tuck the narrow tail end underneath itself so the tenderloin is relatively even in thickness. Tie the roast with kitchen twine at approximately 1 ½-inch intervals.
  • Rub the tenderloin all over with olive oil. Season evenly with salt and pepper.

Sear the Beef

  • Heat a large oven-safe skillet over medium-high heat.
  • Add the tenderloin and sear for 2 to 3 minutes per side, turning as needed until deeply browned all around, including the ends.
  • Remove the skillet from the heat. Spread the softened butter over the top and sides of the tenderloin.

Roast the Beef

  • Transfer the skillet to the oven.
  • Roast for approximately 20 to 30 minutes, checking the internal temperature early rather than relying only on cooking time.
  • For medium-rare, remove the tenderloin from the oven at approximately 125°F. For medium, remove it at approximately 135°F.*
  • Transfer the tenderloin to a cutting board and loosely tent with aluminum foil. Rest for 15 minutes before slicing.

Caramelize the Onions

  • While the beef is roasting and resting, melt 3 tablespoons butter in a large skillet over medium-low heat.
  • Add the onions and ½ teaspoon kosher salt. Toss to coat the onions in the butter.
  • Cook for 35 to 45 minutes, stirring occasionally, until the onions are very soft and deeply golden brown.
  • Reduce the heat if the onions begin browning too quickly. If browned bits build up on the bottom of the skillet before the onions are ready, add a tablespoon of water and scrape them up.
  • Stir in the thyme and cook for about 30 seconds.

Make the French Onion Sauce

  • Increase the heat to medium. Add the white wine, scraping up any browned bits from the bottom of the skillet.
  • Simmer for 3 to 5 minutes, or until the wine has reduced by approximately half.
  • Add the beef broth. Bring to a gentle simmer and cook for 8 to 12 minutes, stirring occasionally, until the liquid has reduced and the onions are coated in a rich, concentrated sauce. The onions should not be swimming in liquid.
  • Remove the skillet from the heat. Add the cold butter and stir until melted and the sauce is glossy.
  • Taste before adding more salt, since the beef broth and Gruyère will contribute saltiness. Add black pepper and additional salt only as needed.

Assemble and Finish

  • Preheat the broiler.
  • Remove the kitchen twine from the rested beef tenderloin. Cut the tenderloin into approximately ½-inch-thick slices.
  • Arrange the slices slightly overlapping on an oven-safe serving platter or in a shallow oven-safe baking dish.
  • Spoon the caramelized onions down the center of the sliced tenderloin, leaving portions of the beef exposed.
  • Spoon a small amount of the reduced sauce over the onions and beef. Reserve the remaining sauce for serving.
  • Sprinkle the shredded Gruyère primarily over the onions.
  • Broil for approximately 1 to 2 minutes, watching constantly, just until the cheese melts and develops a few golden spots.
  • Garnish with fresh thyme, if using. Serve immediately with the remaining French onion sauce on the side.

Notes

*Food Safety Note: The USDA recommends cooking whole cuts of beef to 145°F and letting them rest for at least 3 minutes. Lower temperatures are commonly used for culinary medium-rare preparations.

Nutrition

Serving: 1portion | Calories: 484kcal