Preheat oven to 350 degrees. Line one muffin pan with liners, set aside.
Place sugar in a food processor for about 2 minutes until it becomes fine, almost powder-like. Sift half of the sugar with the salt and cake flour, set aside remaining sugar.
In a large bowl, whisk together egg whites, water, cream of tartar and vanilla. After whisking for approximately 2 minutes, switch to a hand or stand mixer. Gradually sift in the remaining sugar, beating at medium speed until medium peaks have formed.
Add flour mixture a little at a time (you'll want to add it in about 8 additions). It should be just enough flour to dust the top of the peaks. Use a spatula to fold in the dry ingredients in a circular motion, being careful to not deflate the peaks.
Once all of the flour has been folded in, carefully spoon the mixture into the prepared pan, filling ¾ of the way full. Place in oven and bake for 18-20 minutes or until the tops are lightly golden brown (they will also look a bit bubbly). Remove from oven and allow to cool in pan for 5 minutes before transferring to a wire rack to cool completely.
To make the whipped cream, combine all ingredients in the bowl of a stand mixer fitted with a whisk attachment. Slowly bring speed up to high, beat until the cream has reached desired consistency. Pipe or spread on to cooled cupcakes
Notes
-Cupcakes are best served the same day they are baked. -Pipe chilled whipped cream on top of the cupcakes right before serving.