Fill each pastry case with one-quarter of the lemon curd.
In a large, clean bowl, whisk the egg white until it forms soft peaks and hold its shape. Gradually whisk in the sugar, a little at a time, until the mixture is thick and glossy.
Pipe the meringue mixture in swirls over the lemon curd and bake on the top shelf of a preheated oven, 200°C (400°F), Gas Mark 6, for 5–6 minutes or until the meringue is just beginning to brown. Cool slightly and serve.