Let your roast come to room temperature (take out 2 hours before cooking).This step is so important for even cooking. Pat dry with paper towel.
Preheat oven to 460° (430° for convection) Make sure shelf is in the middle of the oven.
Mix together the ingredients for the garlic herb butter.
Place onion, garlic and herbs in the bottom of a cast iron skillet or roasting pan.
Slather on a thin layer of butter in the underside of the beef (bone side). Place beef on top of onion and herbs, butter side down. Spread ²/3 of the butter in the top and sides reserving some for later.
Roast for 20 minutes in the hot oven.
Remove and slather with the remaining butter. Turn oven down to 250°.
Slow roast for 1 hour, basting every 30 minutes until internal temp is 118° in the center (start checking internal temp early). Make sure you don’t pull your roast out at 125° or you will have a medium well piece of meat (nobody wants that!).
Transfer the beef to a cutting board or plate and cover loosely with foil and rest for 20-30 minutes. Internal temp will rise to 125° (medium rare). Do not skip the resting phase. The resting phase allows the juices to redistribute in the meat and it will continue to cook while resting.