Light and marshmallow-like, this frosting is for cakes that do not need refrigeration. This frosting and the Maple Meringue Frosting are of a similar style.
Fill a saucepot with 2 inches (5 cm) of water and bring to a simmer.
In a metal bowl, whisk the sugar, egg whites, cream of tartar, and water. Place the bowl over the pot of simmering water and whisk either by hand or with electric beaters at medium-high speed for 7 minutes. The frosting will turn white and double in volume, but it will still be a bit fluid by