- Preheat the oven to 325°F.
- Sift the flour and granulated sugar twice and set aside.
- Whip the egg whites with the cream of tartar and salt until foamy, then gradually add the icing sugar, whipping until the whites hold a medium peak when the beaters are lifted. Stir in the vanilla.
- Add the flour to the whipped whites in 2 additions and using a whisk to fold in the flour evenly and easily. Scrape the batter into a 10-inch ungreased tube pan, spread it to level and bake the cake for 30-35 minutes, until it springs back when gently pressed (try not to open the oven before 25 minutes).
- Turn the cake pan upside down to cool the cake, and do not remove the cake from the pan until completely cooled. To remove, run a palette knife carefully around the outside of the cake, and very gently around the inner tube, invert the pan and tap it on the counter until it comes out.
- Serve the cake with whipped cream and berries, if you wish.
- The cake will keep, well wrapped (not refrigerated) for up to 3 days.