Heat oven to 250 degrees F.
Draw a 6-inch circle on a piece of parchment paper.
Place on sheet pan, turning over so that the ink is toward the pan but you can still see the circle. Set aside.
With an electric mixer, beat egg whites on medium speed until broken up.
Sift in cornstarch.
Continue beating on medium until foamy.
Stream in sugar slowly.
Increase speed to high.
Beat until medium stiff peaks form.
Add cream of tartar and vanilla.
Continue beating to stiff peaks.
Spoon into circle on prepared parchment.
Smooth sides.
Bake for 1 ½ hours.
Turn oven off. Do NOT open door.
Let stand for an additional 1 hour.
Remove from oven and allow to cool.