Gently heat 600ml / 1 pint of water with the sugar, and stir until the sugar has dissolved.
Add the cinnamon stick or root ginger, then simmer for a few minutes - check it has a good
flavour, then remove the spices and add the chopped rhubarb. Bring to a simmer, cover and cook for
2-3 minutes until just tender, but not collapsing.
Lift out the rhubarb with a slotted spoon and boil the syrup until it is thickened. Stir in the
orange juice and zest, then pour this over the rhubarb and leave to cool. Chill before serving,
topped with whipped cream or crème fraiche.