Potato Flour Sponge cake

9 eggs, separated

1-2/3 cups sugar

1 lemon, rind and juice

1 scant cup potato flour

Beat the yolk til light and creamy, adding sugar gradually. Add grated rind and juice of a lemon, beat thoroughly,

and stir in potato flour a little at a time, beating after each addition. Fold in stiffly beaten egg whites.

Turn into large springform angel food cake pan and bake at 300 deg. at least for 1 hour.

(The recipe says 45-50 minutes, but I found that is not enough. Do not take it out of the oven unless the top springs back when touched).

Cool up-side down, and remove from the pan carefully.