In a large mixing bowl beat the egg yolks until light. Add the sugar and lemon juice and continue beating until very fluffy. Combine the dry ingredients and stirr into the batter. In a separate mixing bowl beat the egg whites until stiff. Fold them into the egg batter. Bake in an ungreased 10 inch tube pan in a preheated 300 degree F oven for 30 minutes. Increase the temperature to 325 degrees F and bake for an additional 15 minutes. Invert to cool
Carrot Cake - Fold 1 cup of grated carrots and 1/2 cup chopped walnuts into the batter before folding in the stiffly beaten egg whites.
Chocolate Chip Cake - Fold 2 ozs grated or finley chopped bittersweet chocolate into the batter before folding in the egg whites.
Marble Cake - Pour 2/3 of the batter into the pan. Add 1- 2 tbs of unsweetened cocoa into the remaining batter. Cut the cocoa to blend. Using a tablespoon, evenly distribute the chocolate batter over the white batter. Cut through the batter several times with a spatula or knife to create the marble effect.
Mocha Cake - Add 3 tbs of instant coffee or 2 tbs instant coffee and 1 tbs unsweetened cocoa to the dry ingredients.
Date-Nute Cake - Add 2 cups finely cut dates, 1/2 chopped nuts and 1 tsp cinnamon to the batter before folding in the egg whites.
Strawberry Shortcake - Split the sponge cake in half. Spread sweetened whipped cream and slice strawberries on the bottom half. Place the second half of the cake on top. Top with whipped cream and whole berries.