My Grandmother made wonderful Angel Food Cakes and sold them. Here is her recipe.
1 Whip the egg whites until foamy. Add cream of tartar, and continue beating until stiff. In a separate bowl, beat the egg yolks until lemon coloured.
2 Boil the sugar and water until it reaches the thread stage, 230 – 234 degrees F (110 – 112 degrees C). Beat syrup into egg whites. Fold in egg yolks. Fold in flour. Pour batter into an ungreased tube pan.
3 Bake at 350 degrees F (175 degrees C) for 1 hour. Cool.