Preheat the oven to 350°F (175°C).
Sift together the cake flour and half of the sugar (½ cup) into a bowl.
In a separate mixing bowl, whip egg whites until foamy, then add cream of tartar and salt.
Continue beating the egg whites until soft peaks form, then gradually add the remaining sugar.
Beat the egg whites until stiff peaks form, then add vanilla and strawberry puree.
Gently fold the flour mixture into the egg whites in three additions.
Pour the batter into an ungreased angel food cake pan, smoothing the top.
Bake for 35-40 minutes, or until the cake is golden brown and springs back when touched.
Immediately invert the pan to cool. Allow to cool completely before removing from the pan.
Once cool, gently run a knife around the edges and invert to release the cake.
Slice and serve plain or with fresh whipped cream and berries, if desired.
