In a food processor, blend the egg and the sugar.
Add the softened butter and pulse until smooth.
Gradually incorporate the sieved flour and salt then pulse until the mixture comes together in a ball.
Remove the dough from the processor and knead a little so it is well combined and has a glossy appearance.
Wrap the dough in cling film and refrigerate for at least an hour.
Whisk the egg yolks and sugar in a bowl.
Add the lemon zest and juice.
Place the bowl over a saucepan of simmering water (bain-marie) and gradually add the butter whilst stirring the curd. The curd will thicken after approximately 20 minutes; remove the bowl from the bain-marie and set aside to cool.
Beat the whites in an electric beater until stiff. Add the cream of tartar, beat, then gradually add the sugar and continue beating for 5 minutes.
Tips and tricks
*The egg whites need to be at room temperature to meringue well.
To assemble and cook the tarts:
Preheat your oven to 180ºC on Bake.
Roll pastry to approx 2mm thick. If you do not have round cutters to make the tart shells use a glass with a thin lip. It may take a few tries to find the right size glass for your tin. Lightly grease a mini muffin tin then line with pastry rounds. Refrigerate the pastry shells (in the tin) for a further 30mins or in the freezer for 10mins.
Blind bake the tart shells for 15 minutes (these are fairly thin and small so they will not take long). When blind baking in mini muffin tins I use a tin foil ball for each shell. I make the balls a little smaller than the shell so when the pastry cooks and expands, it doesn’t close in over the tinfoil. These balls can be reused over and over.
Remove the tinfoil balls (or blind baking beans). Fill the tarts with the lemon curd and bake for a further 5 minutes at 160ºC (if the oven is too hot the lemon curd will boil over).
Pipe the meringue mix onto the lemon tarts and finish in a hot oven (200ºC) to colour the meringue. If I have time, I place the tarts in a hot oven, then turn it off and leave them inside to cool.