To make the meringue: Position the rack in the bottom of the oven and preheat the oven to 300°F. Line 1 large baking sheet with parchment paper and draw an 8-inch circle.
In the bowl of an electric stand mixer fitted with a whisk attachment, beat the egg whites, sugar, vinegar, vanilla, and salt on medium-high speed (#6) for about 18 minutes, or until firm peaks form. Sift the cornstarch into the meringue and gently fold it in.
Using a large spoon, dollop the meringue on the center of the circle on the prepared baking sheet. Spread the batter decoratively, keeping it within the circle (the pavlova will expand when it bakes).
Place the pavlova in the oven and immediately reduce the oven temperature to 225°F. Bake the pavlova for about 1 hour, or until the pavlova is crisp and very pale on the outside but still has a marshmallow-like center. Turn off the oven, prop the oven door open with a wooden spoon, and keep the meringue in the oven for about 30 minutes, or until it has cooled slightly. Remove from the oven to cool completely.
Meanwhile, to prepare the curd, cut the passionfruit in half and scoop their pulp, juice, and seeds into a medium bowl (you should have 2/3 cup). Whisk in the sugar, eggs, and egg yolks to blend. Set the bowl over a saucepan of simmering water and stir constantly for about 5 minutes, or until the mixture thickens. Remove from the heat and gradually whisk in the butter. Cool completely.
To serve, in a large bowl, beat the cream until thick. Set the meringue on a platter. Spoon the cream on top of the meringue. Spoon the curd over the cream. Top with the pineapple, mango, and kiwi pieces.
Cut the pavlova into wedges and transfer to plates. Serve immediately.