Place the prunes in a saucepan with the water, red wine, lemon rind, cinnamon stick and sugar. Cover and simmer for 45-60 minutes until tender. Drain well and reserve the juices.
Remove the stones from the prunes, then purée in a liquidiser or food processor until smooth. Transfer to a mixing bowl and blend in the Armagnac and the cooking juices. Taste and add a squeeze of lemon juice o