For the pastry. Whisk together the butter and sugar then mix in the egg. Fold in the flour and salt and bring together but do not overwork. Wrap in cling film and leave to rest for 1 hour in the fridge
Preheat the oven to 180°C/gas mark 4
Once the pastry has rested, roll it out to a thickness of 3mm and use it to line a 24cm baking dish, letting the edges hang over the edges – these will be trimmed later.
With a fork gently make indentations all over the pastry, but do not go through the pastry.
Scrunch up a sheet of baking paper larger than the dish, and lay it over the pastry
Fill this with baking beads or rice, fold over the top and bake for 10-15 minutes until the pastry on the outer edges is crisp. Remove the baking beads and baking paper and cook for another 10 minutes or so, until the base of the pastry is also crisp. Remove from the oven and leave to cool.
Use a small, serrated knife to trim the edges of the pastry in a gentle sawing motion so as not to shatter it.
For the lemon curd, place the lemon juice and zest in a pan and bring to the boil. Dissolve the cornflour in 80ml water
Mix the sugar, egg yolks and cornflour and stir into the boiling lemon juice, whisking until thickened.
Remove from the heat, beat in the butter a little at a time and cover with cling film.
For the meringue
Place the egg whites in a large clean bowl and begin to whisk with an electric whisk. Start adding the sugar a spoonful at a time until you have a thick, glossy meringue with the smooth texture of shaving foam!
To assemble. Pour the lemon curd into the pastry case and smooth over until it is even. Spoon in the meringue, working from the outside in to create a seal around the edges of the pastry. Swirl the meringue around as you go to ensure you get the nice crispy spikes that we all love.
Bake for 10–15 minutes in the oven, or until the meringue is golden brown and crispy
Leave for 30 minutes before serving or if you prefer to eat it cold, chill in the fridge for a few hours.