Preheat oven to 275°F. Trace eight 3-inch circles on a piece of parchment and set it in a baking sheet.
Whip the egg whites, cream of tartar and salt together until medium-stiff peaks.
Add the water slowly while whipping the whites on low speed. Drizzle in the sugar, then turn up the speed and whip until stiff peaks.
Fold in the vanilla, vinegar and cornstarch. Mound the meringue evenly into the circles on the parchment. Use a spatula to create the design in the meringue. Watch my Instagram video to see how I do this.
Bake at 275°F for 15 minutes or until the meringue starts to turn a very pale tan color, then reduce the heat to 225°F and continue to bake for 30 minutes. Turn off the oven (don't open the door), turn on the light in the oven (don't stress if the light doesn't work) and let the meringue sit in the cooling oven for a couple hours, or even over night.