Preheat the oven to 350 degrees Fahrenheit and place the oven rack to a lower middle position.
Place the sugar in a food processor and pulse until the sugar is fine and powdery. Remove 1 cup of sugar from the food processor and set aside.
Leave the remaining sugar in the food processor and add in the cake flour and salt. Pulse these ingredients together in the food processor until the mixture is combined and light.
Whisk the egg whites and cream of tartar in a large mixing bowl with a stand up or hand held mixer with a whisk attachment until the mixture is light and foamy (approximately 1 minute).
Reduce the mixer speed to medium and slowly add in the 1 cup of sugar that was set aside. Mix until soft peaks are formed (5-6 minutes).
Add in the vanilla extract and mix until just combined.
Gently fold in the flour mixture into the whipped egg whites. Add 1/4 cup of the dry mixture at a time and gently fold in the mixture with a spatula. Continue this process until all of the dry ingredients are mixed in.
Pour the batter into a 9 or 10 inch tub pan (uncreased). Gently tap the pan on a countertop to get out any air bubbles.
Bake for 35-40 minutes until a toothpick inserted into the center of the cake comes out clean and the cake is golden brown.
Remove the cake from the oven. Cool the cake upside down on a wire rack until the cake is completely cooled (2-3 hours).
Run a knife around the edges of the pan (inner and outer). Gently tap the pan on the counter until the cake is released from the pan.
Serve topped with powdered sugar, whipped or fresh berries. Enjoy!