With the rack in the middle position, preheat the oven to 135 °C (275 °F). Line a baking sheet with parchment paper. Set aside.
In a small bowl, dissolve the cornstarch in the vinegar. Set aside.
In a bowl, beat the egg whites with an electric mixer until frothy. Gradually add the sugar, whisking until stiff peaks form. Stir in the cornstarch mixture.
Spread the meringue on the baking sheet, shaping it into a 20-cm (8-inch) disk. Bake for 1 hour and 15 minutes. It will be lightly golden brown. Remove from the oven and let cool completely. It will sink slightly as it cools.
In a bowl, whip the cream and sugar with an electric mixer until soft peaks form. Spread on the cooled meringue and top with the lemon curd (see recipe). Serve immediately.
The meringue must be cooked the same day then garnished just before serving.