Preheat the oven to 110C/220F. Line a large baking sheet with parchment paper.
Add the egg whites and beat together until frothy. Add the cream of tartar and beat until soft peaks form. Add the powdered sugar in, one tablespoon at a time, until stiff peaks form. Transfer the mixture into a piping bag with a star point tip attached.
Pipe out tablespoon portions of meringue onto on the prepared baking sheet. Bake for 45 minutes.
Turn the oven off and slightly open the oven door. Let the meringue cookies cool in there for an hour. After an hour, remove from the oven and let sit at room temperature until cooled.
Notes
TO STORE: Meringue can be stored at room temperature in an airtight container for up to 4 weeks. TO FREEZE: Place the meringue cookies in a ziplock bag and store them in the freezer for up to 6 months. Be sure that the bag is sealed completely, as even a drop of condensation on the cookies will cause them to soften.