Preheat oven to 200F.
Arrange two oven racks to divide oven in thirds.
Line two baking sheets with parchment paper and set aside.
Place egg whites in a large bowl; beat with a mixer at high speed until foamy.
Add cream of tartar and continue to beat until soft peaks form.
Gradually add sugar, 1 tablespoon at a time, beating until egg whites are shiny and stiff peaks form. DO NOT overbeat.
Add vanilla and beat until incorporated.
Pipe or spoon 24 (2-inch-round) mounds onto previously prepared baking sheets.
Place in oven and bake for 2 hours, rotating pans halfway through cooking.
Turn oven off and Cool meringues in oven 40 minutes to 1 hour. (Meringues are done when surface is dry and meringues can be removed from paper without sticking to fingers.)
Remove from oven and carefully remove meringues from paper.