Pour the water into a large saucepan, add the sugar and place over a medium heat. Stir until the sugar has dissolved, and then add the cinnamon stick, lemon rind, lemon juice and rosewater.
Lower the heat and simmer the spiced sugar syrup gently for 10 minutes.
Add the prunes to the syrup and cook gently for 15 minutes.
To make the custard, whisk the egg yolks and sugar together until they are pale and thick.
Pour the milk into a medium saucepan and place over a medium heat. Slit the vanilla pod lengthways and add to the milk. Stirring occasionally, heat the milk to simmering point and then remove from the heat.
Pour the whisked eggs into the hot milk and whisk together gently. Place the pan back on a low heat and keep stirring until the custard has thickened. The custard should coat the back of a wooden spoon when it is done.
Remove the vanilla pod and pour the custard into serving bowls, topped with warm prunes and a spoonful of syrup.