Preheat the oven to 210°C.
Whizz the coating ingredients in a small blender. Make some deep cuts into the lamb and push some of the mix into them, rubbing the remainder all over the skin.
Put the lamb into a roasting tin then add the wine, lemon and onion.
Roast for 20 minutes then turn down the oven to 170°C. Roast for a further 80 minutes, turning the joint occasionally.
Take the joint from the oven and allow to rest, loosely covered with foil, for about 20 minutes before carving.
Meanwhile, whizz the salsa together then serve with the lamb and vegetables of your choice.