Remove the roast from the refrigerator at least two hours before you plan to cook it. This allows the meat to come to room temperature, which ensures it cooks evenly from the edges to the center. Use paper towels to pat the entire surface of the roast completely dry. This step is vital for achieving a good sear and a flavorful crust.
In a small mixing bowl, combine the softened butter, minced garlic, chopped rosemary, thyme, salt, and black pepper. Stir them together until you have a smooth, well incorporated paste. This herb butter will act as both a seasoning and a baste as the fat renders during the roasting process.
Place the roast in a heavy roasting pan with the bone side down. Spread the herb butter mixture generously over all the exposed meat surfaces. Use your hands or a spatula to make sure the coating is even. The bones act as a natural roasting rack, keeping the meat elevated and allowing heat to circulate underneath.
Preheat your oven to 450 degrees Fahrenheit. Place the roast in the oven and cook for 15 to 20 minutes. This high heat blast browns the exterior and locks in the natural juices. Keep a close eye on it to ensure the garlic in the butter rub does not burn, as it should just be golden and fragrant.
Reduce the oven temperature to 325 degrees Fahrenheit without opening the oven door. Continue roasting until a meat thermometer inserted into the thickest part of the roast reaches your desired level of doneness. For medium-rare, aim for 120 to 125 degrees Fahrenheit. This process usually takes about 13 to 15 minutes per pound, but always rely on the thermometer rather than the clock.
Transfer the roast to a cutting board and tent it loosely with foil. Let it rest for at least 30 minutes. While it rests, place the roasting pan on the stovetop over medium heat. Add the beef broth and balsamic vinegar, scraping up the browned bits from the bottom of the pan. Simmer for 5 minutes until slightly reduced, then strain into a small bowl for serving.
