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French Onion Pork Tenderloin - Comforting, Savory, and Simple

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Prep Time 15 minutes
Cook Time 35 minutes
Total Time 50 minutes
Servings: 4 servings
Ingredients Method

Ingredients
  

  • Pork tenderloins: 2 small (about 1 pound each), silver skin trimmed
  • Yellow onions: 3 large, thinly sliced
  • Butter: 2 tablespoons
  • Olive oil: 2 tablespoons, divided
  • Garlic: 3 cloves, minced
  • Beef stock or broth: 1 1/2 cups, low-sodium
  • Dry white wine: 1/2 cup (optional, can sub extra stock)
  • Worcestershire sauce: 1 teaspoon
  • Fresh thyme: 4–5 sprigs (or 1 teaspoon dried)
  • Bay leaf: 1
  • Dijon mustard: 1–2 teaspoons
  • Gruyère or Swiss cheese: 1 to 1 1/2 cups, freshly grated
  • All-purpose flour: 1 tablespoon (optional, for thicker sauce)
  • Salt and black pepper: To taste
  • Smoked paprika: 1/2 teaspoon (optional, for rub)

Method
 

  1. Prep the pork: Pat the tenderloins dry. Season all over with salt, pepper, and smoked paprika. Let sit at room temperature for 15–20 minutes while you start the onions.
  2. Caramelize the onions: Heat a large oven-safe skillet over medium heat. Add butter and 1 tablespoon olive oil. Stir in the sliced onions and a pinch of salt. Cook, stirring every few minutes, for 25–35 minutes until deep golden and jammy. If they brown too fast, lower the heat and splash in a little water to deglaze.
  3. Add garlic and deglaze: Stir in garlic and cook 30 seconds. Pour in wine (if using) and scrape up browned bits. Let it reduce by about half. Add 1 cup of the beef stock, Worcestershire, thyme, and bay leaf. Simmer 5–7 minutes. Taste and season with salt and pepper. Transfer onions to a bowl, leaving some sauce in the pan.
  4. Sear the tenderloins: Return the skillet to medium-high heat and add the remaining tablespoon of olive oil. Sear the pork on all sides until nicely browned, about 6–8 minutes total.
  5. Nestle and roast: Turn off the heat. Spoon most of the onions around and over the pork, reserving a little for topping. Whisk Dijon into the remaining 1/2 cup stock and pour around the pork. Tuck in the thyme sprigs and bay leaf if not already in the onions. Transfer the skillet to a 400°F (200°C) oven and roast 12–18 minutes, or until the thickest part reads 140–145°F (60–63°C).
  6. Rest the meat: Move the tenderloins to a plate and tent loosely with foil for 10 minutes. This keeps the juices in the meat.
  7. Finish the sauce (optional thickening): If you prefer a thicker sauce, bring the onion mixture to a gentle simmer on the stove. Sprinkle in the flour and whisk for 1 minute. Simmer 2–3 minutes until silky. Adjust seasoning.
  8. Slice and top with cheese: Slice pork into medallions, about 1/2 inch thick. Return slices to the skillet, nestling them into the onions. Scatter the reserved onions on top. Cover evenly with shredded Gruyère or Swiss.
  9. Broil to melt: Set the oven to broil. Broil 1–3 minutes until the cheese is melted and bubbly with golden spots. Keep a close eye—it goes fast.
  10. Serve: Spoon saucy onions over each portion. Finish with fresh thyme leaves and cracked pepper. Pair with mashed potatoes, buttered egg noodles, or crusty bread.