Name: Roasted Beef Tenderloin with French Onions and Horseradish Sauce
Prep time: 30 min
Cook time: 45 min
Total time: 1 h 15 min
Cuisine: American
Ingredients: 1 whole beef tenderloin (about 3 pounds); 3 large yellow onions, thinly sliced; 4 tablespoons butter; 2 tablespoons olive oil; 4 sprigs fresh thyme; 3 garlic cloves, smashed; 2 teaspoons kosher salt; 1 teaspoon freshly cracked black pepper; 1/2 cup sour cream; 2 tablespoons prepared horseradish; 2 tablespoons mayonnaise; 1 tablespoon Dijon mustard

Tender, juicy, and packed with savory depth, this Roasted Beef Tenderloin with French Onions and Horseradish Sauce is the ultimate centerpiece for a special dinner or holiday celebration. The buttery beef melts in your mouth, the sweet caramelized onions add rich umami, and the creamy horseradish sauce brings just the right zing to round it all out.

This isn’t just a beef roast—it’s an elevated dish that feels indulgent yet approachable. The prep is straightforward, and with a few chef’s tricks, you’ll pull off a restaurant-worthy meal right from your kitchen. Whether it’s Christmas Eve or a cozy weekend dinner, this tenderloin will win hearts and impress taste buds.

Why You’ll Love This Roasted Beef Tenderloin with French Onions and Horseradish Sauce

Elegant yet easy: Simple steps with big, bold flavors.
Perfect for entertaining: A showstopper that slices like butter.
Flavor-packed: Sweet onions and tangy horseradish play beautifully with the beef.
Make-ahead friendly: Prep the onions and sauce ahead to save time.
Versatile pairings: Pairs well with everything from mashed potatoes to roasted veggies.

Preparation Phase & Tools to Use

Essential Tools and Equipment:

Roasting Pan with Rack: Allows air to circulate around the meat for even roasting and perfect crust.
Cast Iron Skillet: Ideal for searing the tenderloin to lock in flavor before roasting.
Meat Thermometer: Ensures precise doneness (aim for 130°F for medium-rare).
Sharp Carving Knife: For smooth, clean slices of the tenderloin.
Saucepan: Needed for caramelizing the onions and prepping the horseradish sauce.

Each tool contributes to a crucial step: a beautiful sear, a succulent interior, and a sauce that ties everything together. Don’t skip the thermometer—it’s the secret to never overcooking this luxurious cut.

Ingredients for the Roasted Beef Tenderloin with French Onions and Horseradish Sauce

Beef Tenderloin: The star of the show, known for its tenderness and rich beefy flavor.
Yellow Onions: Slowly caramelized to a deep golden brown, adding sweet and savory depth.
Butter: Used to enrich the onions and sear the beef for extra flavor.
Olive Oil: Helps achieve a beautiful sear on the tenderloin.
Fresh Thyme: Adds an earthy aroma that complements the richness of the meat.
Garlic Cloves: Infuses the dish with bold flavor during roasting.
Salt and Cracked Black Pepper: Essential for seasoning every layer.
Horseradish: Brings heat and tang to the creamy sauce.
Sour Cream: The base of the horseradish sauce, providing creaminess and tang.
Mayonnaise: Adds body and smooth texture to the sauce.
Dijon Mustard: Offers a slight sharpness that balances the sauce.

How To Make the Roasted Beef Tenderloin with French Onions and Horseradish Sauce

Step 1: Prep the Tenderloin

Trim the silver skin off the beef tenderloin if not already done. Tie with kitchen twine every 1.5 inches for even cooking. Let it rest at room temperature for 30 minutes.

Step 2: Caramelize the Onions

Slice onions thinly. In a large saucepan, melt butter over medium heat. Add onions, thyme, and a pinch of salt. Cook slowly, stirring often, for 30-40 minutes until deeply golden and jammy.

Step 3: Sear the Tenderloin

Preheat oven to 425°F. Heat olive oil in a cast iron skillet over medium-high heat. Sear the tenderloin on all sides until browned (about 3-4 minutes per side). Transfer to a rack in a roasting pan.

Step 4: Roast to Perfection

Insert a meat thermometer into the thickest part. Roast for about 20-25 minutes or until internal temp reaches 130°F for medium-rare. Rest for 15 minutes before slicing.

Step 5: Make the Horseradish Sauce

Mix sour cream, horseradish, mayonnaise, and Dijon mustard in a small bowl. Season with salt and pepper. Chill until ready to serve.

Step 6: Serve

Top the sliced tenderloin with caramelized onions and a dollop of horseradish sauce. Garnish with fresh thyme for an herby finish.

How to Serve and Store Roasted Beef Tenderloin with French Onions and Horseradish Sauce

Serving Tips:

This dish shines as the centerpiece of a festive dinner. Slice the rested tenderloin into thick medallions and plate with a generous spoonful of caramelized onions and a drizzle of horseradish sauce. Add a few sprigs of thyme for color and aroma. Pair it with sides like mashed potatoes, roasted green beans, or a crisp salad.

Storing Tips:

Store leftover beef in an airtight container in the refrigerator for up to 4 days. For best results, reheat gently in a 300°F oven covered in foil to retain moisture. The horseradish sauce will keep in the fridge for up to 5 days—just give it a quick stir before using. Avoid freezing the sauce, but the beef can be wrapped tightly and frozen for up to 2 months.

Frequently Asked Questions

How do I keep the beef tender and not overcooked?

Use a meat thermometer and remove the beef at 130°F for medium-rare. Let it rest to retain juices.

Can I make the caramelized onions ahead?

Yes! You can prepare them a day in advance and reheat gently on the stove.

Is there a substitute for horseradish in the sauce?

You can use wasabi or a touch of spicy brown mustard, though it will slightly change the flavor profile.

What wine pairs well with this dish?

A bold red like Cabernet Sauvignon or Syrah enhances the richness of the beef and the sharpness of the sauce.

Can I use another cut of beef?

If tenderloin isn’t available, a center-cut sirloin roast can be used, though it will be slightly less tender.

Do I need to tie the tenderloin?

Yes, tying the roast ensures even cooking and helps maintain its shape while roasting.

Want More Beef Dinner Ideas with a Twist?

If this Roasted Beef Tenderloin with French Onions and Horseradish Sauce has won your heart, you’ll definitely want to check out these other delicious beef recipes from the blog:

Garlic Butter Beef Cheesy Bowtie Pasta for a rich, weeknight-friendly dish.
French Onion Ground Beef and Rice Casserole for cozy comfort food with similar oniony vibes.
Effortless Philly Cheesesteak Meatloaf when you’re craving all the sandwich flavor in a sliceable form.
Sticky Honey Garlic Steak Rotini for a saucy, sweet-savory twist.
Beef and Rotini in Garlic Parmesan Sauce for a creamy pasta pairing that’s always a crowd-pleaser.

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Let me know in the comments how your tenderloin turned out! Did you add extra herbs or try a different sauce twist? Maybe blue cheese instead of horseradish? I’d love to hear how you made it your own.

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