Combine raspberries, sugar, lemon zest, port and 1 cup of water in a medium saucepan. Bring mixture to a boil, stirring frequently. Reduce heat, cover and simmer for 10 minutes. Stir in tapioca and bring back to a boil. Reduce heat and cook until thick and translucent, stirring constantly. Let cool.
Spoon into 4 dessert dishes and refrigerate until completely chilled, at least 2 hours. Just before serving, whip the cream with the confectioners' sugar until stiff. Spoon on top of pudding and serve.