Preheat the oven to gas mark 6/200°C. Grease a roasting tray with 2 tablespoons of oil. Rub the butter and salt over the venison and place in the tray.
Clean the beetroots but don’t peel them. Put them around the joint in the tray and roast for 30 minutes.
Check the beetroots: if a fork or skewer meets little resistance they are ready. Remove them from the tray, put in a bowl and cover with clingfilm or a plate.
Return the venison to the oven for a further 15 minutes. Once the beetroots have cooled a little, remove the skins. Slice and set aside.
Remove the venison from the oven. Rest for 15 minutes before carving. Slice the cooled meat as thinly as possible and serve with the beetroots.
Served with a Bourgogne wine such as Gevrey Chambertin, Pommard or Clos de vougeot.