cast iron steaks with french onions

French Onion Filet Mignon

Last Updated on August 21, 2023

French onion soup is so rich and luscious, and so is filet mignon. Why not put them together?

Transform the flavors of the soup into a luxurious topping for filet and you have a dressed-up meal that’s easy to make but feels special, perfect for an intimate date night at home. Pour some wine, light a candle, and enjoy.


French Onion Filet Mignon

3.69 from 41 votes
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Protein: Beef
Cut: Filet Mignon
Course: Main Course
Prep Time: 10 minutes
Cook Time: 40 minutes


  • 2 ButcherBox filet mignons 4 to 5 ounces each
  • 1 tablespoon unsalted butter
  • 2 tablespoons oil, for cooking (We prefer cooking with avocado oil.)
  • 1 medium yellow onion sliced
  • Fine sea salt
  • ¼ teaspoon honey
  • 1 teaspoon minced fresh sage
  • Freshly ground black pepper
  • 1 teaspoon arrowroot
  • 3 tablespoons beef bone broth
  • 3 tablespoons shredded gruyere


  • Remove steaks from the fridge and allow them to come to room temperature.
  • Melt butter with 1 tablespoon oil in a large skillet over medium heat. Add onion, sprinkle with salt, and cook, stirring occasionally, until tender, about 5 minutes. Add honey and continue to cook, stirring occasionally, until deeply caramelized—25 to 30 minutes. Add sage and cook for 10 more minutes. Watch the onions carefully and add a tablespoon or two of water or broth if they get too dry or start to cook unevenly.
  • While onions are cooking, prepare steak: Preheat the oven to 425ºF. Warm a cast-iron skillet over high heat until hot. Pat steaks dry; season generously with salt and pepper. Add remaining 1 tablespoon oil to the skillet. Add steaks and sear until nicely browned on both sides, 2 to 3 minutes per side.
  • Transfer to the oven and cook until an instant-read thermometer stuck into the thickest part of a steak reads 130ºF, 5 to 10 minutes (depending on thickness). Remove the skillet from the oven. Transfer steaks to a cutting board; cover and let rest for 5 to 10 minutes.
  • Whisk arrowroot into broth until incorporated. Reduce heat on stove to medium-low. When onions have caramelized, add broth mixture one tablespoon at a time and cook, stirring, until the mixture has the consistency you want. Sprinkle with cheese and continue to cook, stirring, until the sauce has thickened and the cheese has melted—about 1 minute.
  • Place each steak on a plate. Top each with half of the onion mixture and serve.
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Beth Lipton is a Brooklyn-based recipe developer and writer specializing in food and wellness. Her work has appeared in Clean Eating, Paleo magazine,, Well+Good, Outside, and more. Beth's latest cookbook, Carnivore-ish, featuring 125 animal protein-forward recipes, is available now.