I was so nervous to make this recipe because the directions called to, "beat until stiff peaks form". My experience trying that has always not gone over well, but this time it worked out!! You really do have to blend for a while... maybe 15 minutes or so. This was so good, it was definitely worth the anxiety!
1-1/4 C powdered sugar
1 c cake flour (I substituted all purpose flour which was 1 c minus 2 Tbsp)
1 1/2 t cream of tartar
1 1/2 t vanilla
1 c granulated sugar (I added about 1/2 cup extra sugar)
Move oven rack to lowest level. Heat oven to 350. After separating eggs, let rest at room temperature for 30 minutes. In second bowl, combine powdered sugar and flour. Sift mixture three or four times.
In large mixing bowl, add cream of tartar, vanilla, and salt to egg whties; beat on high speed. Add granulated sugar, beating until sugar is dissolved and stiff peaks form. Add dry ingredients into egg mixture 1/4 cup at a time, folding in by hand after each addition.
Gently spoon batter into an ungreased 10 inch angel food cake pan. Cut through batter with a knife to break up air bubbles. Bake at 350 for 40-45 minutes or until cake springs back to the touch. Invert pan to cool to prevent collapse of cake. (if pan doesn't have its own stand, balance pan on a glass bottle.) Cool for at least an hour. Turn cake over; use a large serrated knife to loosen sides of the cake. Invert again over large plate or serving tray. Serve with whipped cream and blueberries.