Beef Tenderloin with Caramelized Onion-Red Wine Sauce | Daily Life at Five Marys!

Ingredients

• 2 tablespoons extra-virgin olive oil
• 3 cloves garlic, minced
• 1 tablespoon M5 spice rub or 1 tablespoon kosher salt
• 1 teaspoon freshly ground black pepper
• 2 teaspoons minced fresh thyme leaves
• 3-pound center-cut beef tenderloin roast, trimmed of silver skin
• 6 tablespoons unsalted butter, divided
• 2 large yellow onions, halved and thinly sliced
• Kosher salt and freshly ground black pepper
• 2 cups full-bodied red wine
• 1 cup low-sodium beef stock
• 3 sprigs fresh thyme
• 1 tablespoon balsamic vinegar
• 2 teaspoons packed light brown sugar