Preperation

In the bowl of a stand mixer, whisk together 1/4 cup of water, sugar, egg whites, cream of tartar and salt.

Set bowl over a pot of simmering water whisk the mixture until it is very warm. Remove bowl from the pot.

Beat until frosting is stiff and cooled, about 5-7 minutes. Beat in vanilla.

If all went well, you should see something that looks like this...

FROM_JS