Roasted Beef Tenderloin with French Onions and Horseradish Sauce

Alright, friends, let me tell you—this roasted beef tenderloin is the kind of dish that gives you all the feels. Picture this: a beautifully browned, juicy tenderloin that practically melts in your mouth, paired with the deep, sweet richness of caramelized French onions and a zesty horseradish sauce that adds just the right kick. Honestly, every time I make this, my kitchen fills with those irresistible aromas—the butter sizzling, the onions slowly turning golden, the tenderloin roasting to perfection. It’s a dish that looks fancy but is surprisingly straightforward to pull off, making it perfect for impressing guests or just treating yourself on a cozy weekend. Trust me, once you try it, it’ll become one of your go-to recipes for any special dinner.

Quick Facts

• Yield: Serves 6
• Prep Time: 20 minutes
• Cook Time: 45 minutes
• Total Time: 1 hour 5 minutes

Ingredients

For the Main Dish:

• 2 ½ to 3 lb beef tenderloin, trimmed
• 2 tbsp olive oil
• 1 tsp kosher salt
• ½ tsp freshly ground black pepper
• 3 tbsp unsalted butter
• 1 large yellow onion, thinly sliced
• 2 cloves garlic, minced
• 1 tsp fresh thyme leaves (or ½ tsp dried thyme)

For the Horseradish Sauce:

• ½ cup sour cream
• 2 tbsp prepared horseradish (adjust to taste)
• 1 tsp Dijon mustard
• ½ tsp lemon juice
• Salt and pepper, to taste

How I Make It

Step 1:

First up, preheat your oven to 425°F. Pat the beef tenderloin dry with paper towels—this step helps you get that gorgeous crust. Rub the olive oil all over the meat, then season generously with kosher salt and black pepper. Let it rest at room temperature for 15 minutes while you get the onions ready.

Step 2:

In a large skillet, melt the butter over medium heat. Add the sliced onions and a pinch of salt, then stir occasionally for about 15 minutes until they are soft and a rich golden brown. Stir in the minced garlic and thyme, cooking for another 1–2 minutes until fragrant. Remove from heat and set aside.

Step 3:

Place the tenderloin on a roasting rack set inside a baking pan. Roast in the preheated oven for about 35–45 minutes, or until an instant-read thermometer inserted into the thickest part reads 130°F for medium-rare. (If you prefer a different doneness, aim for 125°F for rare or 140°F for medium.)

Step 4:

Once done, remove the tenderloin from the oven and tent it loosely with foil. Let it rest for at least 15 minutes—this step is crucial for juicy slices.

Step 5:

Meanwhile, mix the sour cream, horseradish, Dijon mustard, lemon juice, salt, and pepper in a small bowl. Taste and adjust the horseradish level if you want more punch. Keep it chilled until serving.

Step 6:

Slice the rested tenderloin into thick medallions. Serve on a warm platter topped with spoonfuls of the caramelized French onions and a dollop of the horseradish sauce on the side. The colors and flavors will make your guests swoon!

Variations & Tips

• For an extra herbaceous note, add fresh rosemary or sage to the buttered onions.
• If you want to amplify the crust, sear the tenderloin in a hot cast-iron skillet for 2 minutes per side before roasting.
• Use shallots instead of onions for a milder, slightly sweeter onion flavor.
• For low sodium, reduce the salt and use fresh herbs to boost flavor.
• Make the horseradish sauce a day ahead for deeper flavor; keep it covered in the fridge.
• Resting the beef uncovered helps keep the crust crispy, but tenting prevents heat loss—balance it based on your preference.

How I Like to Serve It

This beef tenderloin shines on holidays or special Sunday dinners when you want to impress with minimal stress. Pair it with roasted garlic mashed potatoes or buttery green beans. For fall or winter meals, add a side of roasted root vegetables and a robust red wine, and you’re set for a cozy, elegant feast.

Notes

• Store leftovers wrapped tightly in the fridge for up to 3 days; reheat gently in a low oven to avoid overcooking.
• If horseradish isn’t your thing, swap with creamy horseradish-free mustard sauce or a simple chimichurri.

Closing: This recipe strikes that perfect balance of elegant and approachable, making it a reliable champion on your dinner table every time.