Preheat your oven to 220°C/Fan 200°C/Gas 7. Unwrap your beef. Pat dry. Bring the meat up to room temperature.
Peel and grate or crush the garlic. Mix it with 1 tsp of the ras el hanut, a little salt and pepper and 1/2 tbsp olive oil. Rub it all over the beef joint. Pop it in a snug roasting tin.
Cut two squares of foil to cover the cut sides of the beef to keep them moist, allowing just the fat to be directly exposed to the heat. Pop in the centre of the oven, middle shelf. Turn the heat down to 180°C/Fan 160°C/Gas 4. Roast for 45 mins for rare, 1 hr for medium and 1 hr 15 mins for well done.
See our How to Cook the Perfect Steak video for tips on testing the doneness without cutting into your joint, as you want to give it a good long rest (at least 30 mins, longer if poss) before carving. Whip up your sides while it relaxes.
Thinly slice the beef. Cut out any stringy bits. Arrange on a platter. Reheat the pan juices from the beef and drizzle them over the top. Dust with a little salt and 1/2 tsp ras el hanut. Serve up.