Preheat oven to 250°F (120°C) and line a baking sheet with parchment paper.
Beat egg whites until foamy, then gradually add sugar while beating until stiff peaks form.
Fold in vinegar, cornstarch, and vanilla gently.
Pipe or spoon 6-8 mounds onto the baking sheet, forming small nests.
Bake for 80-90 minutes, then turn off oven and let meringues cool inside for at least 1 hour.