Combine flour, 1/2 cup sugar, baking powder and salt in small mixing bowl. Make a well in center; add egg yolks, oil and water and vanilla. Beat at high speed for 5 minutes or until satiny smooth.
Combine egg whites and cream of tartar in a large metal mixing bowl. Beat until soft peaks form. Add 1/2 cup sugar, 2 tablespoons at a time. Beat about 4 minutes at medium speed until very stiff peaks form. Peaks should stand straight up when beaters are lifted.
Note: If you wipe the bowl with lemon juice or vinegar just before starting to beat the whites, you will find that the whites will more easily come together. Be sure the bowl is very clean and the eggs are at room temperature. A pinch of cream of tartar helps to stabilize the eggs. It’s important, in this recipe, that no egg yolk be mixed in with the egg whites or on the bowl or beaters.
Pour egg yolk mixture in a thin stream over entire surface of egg whites, gently folding mixture, into whites. Pour batter into ungreased 10″ tube pan, spreading batter evenly with spatula.
Bake at 325°F for 1 hour or until cake springs back when touched lightly.
Remove from oven, invert cake while still in pan, and cool completely upside down before removing from pan. This helps the cake to gently detach from the pan while cooling.
If at all possible, bake the cake the day before assembling. If this isn’t an option make certain to allow the cake to cool completely and set before filling and frosting.
* I used Pamela’s Bread and Baking Mix. Use a 1 – to- 1 gluten-free baking mix you are comfortable with.