Preheat the oven to 180C/350F/Gas 4.
For the cupcakes, cream the butter, sugar and vanilla seeds together in a large mixing bowl until pale, fluffy and well combined.
Crack in the eggs, one at a time, and beat until both are fully incorporated into the mixture.
Fold in the flour and lemon zest until well combined.
Place 12 paper or foil cupcake cases into the wells of a muffin tray, then spoon in the cupcake batter. Add a teaspoonful of lemon curd to the top of each cupcake.
Bake the cupcakes in the oven for 15-20 minutes, or until they are pale golden-brown and spring back when pressed lightly in the centre.
Meanwhile, for the meringue, whisk the egg whites until soft peaks form when the whisk is removed. Gradually add the sugar, whisking continuously, until stiff peaks form when the whisk is removed and the mixture is thick and glossy.
When the cakes are cooked, turn off the oven and preheat the grill to its highest setting.
Spoon the meringue over the cupcakes and tease it into spikes using a fork. Place the cupcakes under the hot grill for 2-3 minutes, or until the meringue is golden-brown.