For the pastry place the flour and sugar in the largest bowl of the food processor and pulse quickly to combine. Add the butter and process to fine breadcrumbs.
Add the egg yolk and 1 tbsp of water and process until the mixture forms a ball. If the pastry is still crumbly, add the remaining tbsp of water.
Remove the pastry and gently knead into a disc, wrap in cling film and chill for a minimum of half an hour.
Pre-heat the oven to 180ºC. Remove the pastry from the fridge, roll out and line a 21cm deep fluted tart tin with a loose base. Prick the base with a fork and line with greaseproof paper then fill with baking beans. Bake for around 15 minutes until the pastry is set.
Remove the baking beans and return to the oven for a few minutes to dry out. Remove the pastry from the oven and leave to cool. Reduce the oven temperature to 150ºC.
For the passion fruit curd, remove the pulp from the passion fruit and process in the smallest bowl of the food processor. Pass the pulp through a sieve into a measuring jug and discard any seeds. Add the lime juice and zest then pour in cold water to make up to 300ml.
Place the passion fruit juice, 3 tbsp cornflour and sugar into a saucepan and heat, stirring continuously until the mixture thickens to a curd like consistency. Take off the heat, leave to cool for a minute and then whisk in the 4 egg yolks and butter. Keep warm.
For the meringue, whisk the egg whites to soft peaks and then slowly add the sugar a spoonful at a time, making sure you incorporate fully after each addition. Once all the sugar is dissolved and the mix is stiff and glossy, add 2 tbsp cornflour and whisk again to incorporate.
Pour the warm passion fruit curd into the pastry shell and spoon or pipe, starting from the outside, the meringue mixture on top, ensure you create a seal with the pastry around the edge.
Bake in the oven for 20-25 minutes until the meringue is set and golden brown. Leave to cool in the tin for half an hour. Remove from tin then chill for a further 2 hours.