Place butter and plain flour into the large mixing bowl, or into the bowl of a stand mixer, mix for 2 mins on mid speed (speed 2).
Add the icing sugar and egg and mix again for 1 min, (speed 2) until the pastry starts to form.

Cover the pastry with plastic wrap, refrigerate for 30 minutes.

Prepare the lemon curd - add the lemon juice, sugar, eggs and egg yolk, into a heatproof bowl placed over a saucepan, filled to 1/3 with gently simmering water.
Cook the curd for 20 minutes on high heat, whisking continuously.
Once the curd is very thick, remove from heat and add the cubed butter.
Allow the butter to sit for 2 minutes before stirring until completely melted.
Sieve the mixture into a separate bowl to remove any lumps, cover the curd with plastic wrap and refrigerate until required. 

Grease the 8 inch fluted tart tin.

Remove the pastry from the fridge and roll out to 3mm on a lightly floured surface.

Line the tin with the pastry, trim and excess from the edges.

Use a fork to prick the base of the tart to prevent it from rising.

Transfer the pastry case into the fridge for 20 mins.

Cover the tart with baking paper and fill with baking beans.

Transfer the tart to the drawer and select the OVEN function, CAKE, 160°C, set 25 minutes and press the START button.

Bake the tart for about 15 minutes. Carefully remove the baking beans and baking paper, then bake again for another 10 minutes until golden. 

Remove the tart from drawer, allow to cool completely in the tin. 

Remove the lemon curd from the fridge, transfer the lemon curd into the tart and spread evenly. Transfer the tart into the fridge to set while you make the meringue. 

In a large mixing bowl, or the bowl of a stand mixer, whisk the egg whites for 1 min, speed max.
After 1 minute, while mixing, gradually add the sugar (200 g) and continue mixing for a further 4 minutes, speed max until you have a stiff, glossy meringue. 

Remove tart from fridge.
Place spoonfuls of meringue around the edge of the tart, if you start in the middle, the meringue may sink, spread it out so that it just touches the pastry edge, this will anchor it and help stop it sliding.

Carefully place the pie into the drawer, select OVEN function, cake, 140°C for 20 minutes. Once cooked, select 160°C for a further 5 minutes to brown the meringue.

Once cooked, open the drawer slightly and allow the pie to sit inside the airfryer with the drawer open for 30 minutes, to cool very slowly.

Transfer to a cooling rack after this time to cool completely.
Refrigerate the pie for 30 minutes before serving.