Oven-Roasted Beef Tenderloin with Creamy Caramelized Onion Sauce

Name: Oven-Roasted Beef Tenderloin with Creamy Caramelized Onion Sauce
Prep time: 60 min
Total time: 60 min
Yield: 8 servings
Cuisine: Française
Ingredients: 700 g (1.5 lb) whole beef tenderloin; 2 medium yellow onions, sliced into rings; 2 medium red onions, sliced into rings; 1 garlic clove, finely minced; 1 tsp fine salt; 2 tbsp mayonnaise (for the crust); ½ cup (125 ml) mayonnaise (for the sauce); ½ cup (125 ml) water; Fresh flat-leaf parsley, chopped, to garnish; Aluminum foil

By Marie Lefebvre · Updated October 25, 2026

A whole beef tenderloin roasted to golden perfection under a savory garlic-mayo crust, then served with a silky sauce built from pan drippings and sweet roasted onions. Impressive on the table, surprisingly simple to make.

Prep⏱️ 60 min

Servings👥 8 servings

Difficulty📊 Easy

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🛒 Ingredients

8 servings

700 g (1.5 lb) whole beef tenderloin
2 medium yellow onions, sliced into rings
2 medium red onions, sliced into rings
1 garlic clove, finely minced
1 tsp fine salt
2 tbsp mayonnaise (for the crust)
½ cup (125 ml) mayonnaise (for the sauce)
½ cup (125 ml) water
Fresh flat-leaf parsley, chopped, to garnish
Aluminum foil

🛍️ Recommended tools

🥩Poêle fonteSee on Amazon →🌡️Thermomètre sondeSee on Amazon →🔪Couteau de chefSee on Amazon →

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Directions

1
Preheat your oven to 350 °F (180 °C).
2
In a small bowl, combine the minced garlic, salt, and 2 tbsp of mayonnaise. Rub this mixture all over the surface of the beef tenderloin, coating it evenly.
3
Place the tenderloin in a medium roasting pan (13 × 9 in) and scatter the onion rings around it. Cover tightly with aluminum foil and bake for 20 minutes.
4
Remove the foil and roast for another 20 minutes until the surface is deeply golden. Transfer the beef to a cutting board, set the onions aside, and let rest 5 minutes before slicing.
5
Set the roasting pan over low heat on the stovetop, add the water, and scrape up the caramelized bits with a wooden spoon. Strain the liquid through a fine sieve into a small saucepan.
6
Add the reserved roasted onions and the ½ cup of mayonnaise. Stir well and simmer over low heat for 5 minutes, stirring constantly, until the sauce is smooth and creamy.
7
Arrange the sliced beef on a serving platter, spoon the onion sauce generously over the top, scatter fresh parsley and serve immediately.

💡 Chef's Tip

Rest the beef 5 minutes before slicing to keep it juicy. Swap parsley for fresh chives or thyme for a different finish. A teaspoon of Dijon mustard stirred into the sauce adds great depth.