Preheat oven to 140C (120C fan-forced). Remove the base from a 22-24cm springform tin and set aside. Line the sides with baking paper, coming up a few centimetres above the edge. Place on a flat oven tray lined with paper.
Whip egg whites until soft peaks form. With the beaters running, add caster sugar one spoonful at a time, mixing well in between each addition. This will take some time, but is important for the finished result. Add the cornflour in with the last spoonful of sugar. Continue mixing for 5-10 minutes until the sugar has dissolved completely. You can test this by rubbing a little of the mixture between a finger and thumb - it should be completely smooth. Add lemon juice and vanilla and continue mixing for another minute.
Spoon into prepared tin (the meringue will be sitting directly on the lined tray), smoothing down the top evenly. Place in the oven and bake for 1.5 hours. Without removing pavlova, turn off oven, open the door slightly and allow to cool for a couple of hours or overnight.
To make filling: beat cream until thick. Set aside. Dissolve gelatine in 1/4 cup boiling water. Set aside. Whip together cream cheese with caster sugar until smooth. Add dissolved gelatine and strained passionfruit and beat well. Fold through whipped cream.
Spoon filling into tin on top of pavlova base, pushing it right to the edges and smoothing out evenly on top. Refrigerate for 4 hours to set completely.
Just prior to serving, remove from fridge. Tilt tin and carefully remove paper from base, then place on serving platter. Unlock spring and carefully remove tin - you may need to first slide a knife around between tin and paper to unstick it. Pull off paper. Spread extra whipped cream around the sides to cover any imperfections. Top with fruit and serve.