8 large egg whites
1 1/3 cup sugar
2 tsp cream of tartar
1 tsp vanilla extract
Fill the bottom of a medium saucepan with water and bring to a simmer.
In the bowl of an electric mixer, combine the egg whites with the sugar and the cream of tartar. Place over the saucepan and whisk constantly until the sugar is dissolved and mixture is warm to the touch, about 3 minutes. To check if the sugar is completely dissolved, rub the whites between your fingers.
Transfer the bowl to the electric mixer stand fitted with the whisk attachment, and whip on low speed. Increase the speed gradually to high and keep whipping until the whites are shiny and form stiff peaks, about 10 minutes.
Add the vanilla and mix until combined.