Preheat the oven to 180°C and line a tray with greaseproof paper.
Whisk sugar gradually into stiff egg whites until the mixture is smooth and glossy.
Gently fold the sherry vinegar into the meringue mixture.
Spoon the meringue onto the tray in a 20cm circle with dollops around the edges.
Reduce oven to 150°C and bake for 45-50 minutes until the outside has hardened.
Whisk citrus juice, zest, sugar, eggs, yolks, and 75g butter in a pan over medium heat.
Stir in the remaining butter continuously until the mixture thickens considerably.
Remove the curd from heat and let it cool completely.
Fill the meringue centre with curd and top with whipped cream and passion fruit.