Remove your roast from the fridge about 30–60 minutes before you begin. This helps it reach room temperature and promotes even roasting.

Preheat your oven to 450°F (230°C).

In a small bowl, mix the extra-virgin olive oil, Dijon mustard, chopped rosemary, minced garlic, 1 teaspoon salt, and 1 teaspoon pepper.

Pat the roast dry with paper towels. Rub the mixture all over the surface of the roast—make sure you coat every side so the flavor penetrates.

On a baking sheet (or roasting pan) place the quartered red onions around the roast. Sprinkle the remaining ½ teaspoon salt and ½ teaspoon pepper over the onions. Scatter the dark brown sugar over the onions and roast too.

In a separate small bowl mix the dry red wine and balsamic vinegar. Drizzle that mixture around and under the roast (not directly over the top so you don’t wash off the rub).

Insert a meat thermometer into the thickest part of the roast (away from bone if it has one).

Place the roast in the oven and sear it at 450°F for 15 minutes. This high temperature gives that nice brown crust on the outside.

After 15 minutes, reduce the oven temperature to 350°F (175°C). Continue roasting until the internal temperature reaches about 125°F-130°F (52-54°C) for medium-rare, or 135°F (57°C) for medium. (It will rise a few degrees while resting.) For a 3- to 4-pound roast you’re looking roughly 40-60 more minutes—monitor with your thermometer.

Once target temperature is reached, remove the roast from the oven. Tent it loosely with foil and let it rest for 15-20 minutes. Resting is key so the juices redistribute and the texture holds.

After resting, slice the roast against the grain into roughly ½-inch thick slices. Serve with the roasted onions and pan juices.