In the beginning, combine together the sugar, water, egg whites, cream of tartar, and salt in a medium glass bowl.
You’ll want to set a saucepan of water on the stove to come to a simmer. with an electric mixer on low, in the meantime, beat egg mixture for about 30 seconds. Immediately set bowl over simmering pan of water, forming a double boiler, beating constantly on high until stiff and glossy, about 7 minutes.
Once done, you can remove from heat, add vanilla, and beat for an additional 1 to 2 minutes. Make sure to use directly, frosting will set quickly.
