In a large mixing bowl, beat the egg whites at low speed for about 1 minute, until the whites are loose and have begun to foam. Increase speed of mixer to high; gradually add the sugar and continue beating for at least 5 minutes.
Add the yoks and lemon juice, continue beating. Sift the cake meal with the potato starch; add to the mixing bowl. Beat until thoroughly blended.
Turn the batter into an ungreased 10-inch tube pan and bake in a preheated 350 degree oven for 1 hour and 10 minutes.
Invert to cool for at least 1 hour.
Serving suggestions: This may be served plain, frosted, with a sauce, or topped with whipped cream and fruit. If this or any sponge cake should get stale, use it for Passover French Toast or cut it into1 inch slices and toast until golden and serve hot with chocolate sauce or ice cream. You can sandwich ice cream between slices and serve with a heated sauce.