Preheat the oven to 275F. Trace a circle 8-inches across using marker on parchment paper, then flip the paper over onto a baking tray.
Whip the egg whites first on low speed, then once the whites are foamy increase the speed and slowly pour in the sugar while whipping. Continue to whip until the whites on high speed until they hold a firm peak when beaters are lifted. Stir the cornstarch and cream of tartar together and fold this into the meringue by hand, then fold in the vanilla.
Dollop the entire meringue into the centre of the drawn circle and spread using a spatula, creating an upwards “swoosh” from the base to create lines going up (this gives the pavlova a pretty shape).
Bake the pavlova for about 60 to 90 minutes – it will still seem soft on the outside when warm, but if the meringue does not cool to have a crunchy exterior, you can return the meringue to the oven for an additional 15 to 30 minutes (the outdoor temperature and humidity impacts the bake time). If the pavlova begins to brown, crack open the oven door and continue baking. Cool the pavlova completely on the baking tray.
For assembly, whip the cream to a soft peak and fold in the lemon zest, lemon juice and then the sugar. Gently lift the pavlova (using the bottom of a removable bottom tart pan works well) onto your serving plate, then spoon the whipped cream over top, spreading it, but not quite to the edges. Cut the ripe passion fruits in half and scoop out the seeds and juice, spooning this overtop of the cream.
The pavlova meringue can be baked hours ahead, but should be assembled right before serving.