Line a flan tin with the pastry. Line the centre with greaseproof paper, weight it down with crusts or dried beans, and bake at 425° F., gas mark 7, for 10 minutes.
For the filling use a double saucepan – or a basin or saucepan which will fit into a large one containing boiling water. Put the sugar into the small saucepan or basin. Grate the lemon rind into it, then squeeze in the juice