Preheat the oven to at 225 degrees F/ 110 degrees C.
In a clean bowl, whip the whites and salt into soft peaks, add the vanilla, and continue beating to stiff peaks. Stir the cream of tartar into the regular sugar and whisk into the whites very gradually, a spoonful at a time, until the meringue is stiff and the sugar has dissolved. Sift together the icing sugar and cornstarch. Sift over the meringue and gently fold until fully incorporated.
Pipe or spoon the meringues onto a parchment-lined baking sheet. Bake until cream-colored and crisp on top when tapped, 1 to 1 and a 1/2 hours. Remove from the oven. Cool on the trays. Store in an air-tight container.