Beef Tenderloin With Caramelized Onion–red Wine Sauce

Let's Cook

1. Step 1.

   In a small bowl, stir together 2 tablespoons extra-virgin olive oil, 3 minced garlic cloves, 1 tablespoon M5 Spice Rub (or 1 tablespoon kosher salt and 1 teaspoon black pepper), and 2 teaspoons minced fresh thyme. Place the 3-pound center-cut beef tenderloin roast on a baking sheet and rub the herb mixture all over the meat. Using kitchen string, tie the roast every 1½ inches to help it hold its shape. Cover and let stand at room temperature for 1 hour (or refrigerate up to overnight; if refrigerated, let stand at room temperature for 1 hour before cooking).

2. Step 2.

   Preheat the oven to 425°F. Place a wire rack in a shallow roasting pan just large enough to hold the tenderloin. Roast the tenderloin until deeply browned and an instant-read thermometer inserted into the center registers about 125°F for medium-rare, about 45 minutes. Remove the pan from the oven and transfer the tenderloin to a cutting board. Tent loosely with aluminum foil and let rest for 15 to 30 minutes.

3. Step 3.

   While the tenderloin rests, make the sauce. In a large skillet over medium heat, melt 2 tablespoons of the unsalted butter. Add the 2 thinly sliced yellow onions and a big pinch of salt. Cook, stirring occasionally, until the onions are golden and caramelized, 15 to 20 minutes (reduce the heat slightly if they brown too quickly).

4. Step 4.

   Add 2 cups full-bodied red wine, 1 cup low-sodium beef stock, and 3 sprigs fresh thyme to the skillet. Increase the heat to medium-high and bring to a boil. Boil until the liquid reduces by half, about 10 minutes (reduce the heat to medium if boiling too rapidly). Stir in 1 tablespoon balsamic vinegar and 2 teaspoons packed light brown sugar, and cook for about 1 minute longer. Cover the sauce and set aside to keep warm.

5. Step 5.

   When ready to serve, remove the thyme sprigs from the sauce. Reheat the sauce over medium-low, then whisk in the remaining 4 tablespoons unsalted butter, 1 tablespoon at a time, until emulsified. Remove from heat, stir in any juices that have accumulated on the cutting board from the resting tenderloin, and season with salt and pepper to taste.

6. Step 6.

   Cut the tenderloin across the grain into thick slices. Arrange the slices on a platter, top with the warm sauce, and serve at once.