In the bowl of an electric mixer, combine cake flour, sugar, baking powder, and salt.

Add oil, egg yolks, and orange juice. Beat at medium-high for 3 to 4 minutes or until smooth. Stir in zest.

Add the cream of tartar to the egg whites.

Beat until stiff peaks form.

Gently fold the egg whites into the batter.

Here is how I get my cakes to be nice and flat. You need 2 (9-inch) cake pans, a baking sheet, and Bake Even strips.

Spray the pans with baking spray. Or you can butter and flour them, I am lazy and don't bother to do that. Get the strips nice and wet. Wrap them around the cake pans. Place both cake pans on the baking sheet. You do not need to put them on the baking sheet, but I think that it is easier to get them in and out of the oven.

Divide batter evenly between the pans.

Bake in a preheated 350-degree oven for 22 to 27 minutes, or until a toothpick comes out clean.

Cool in pans for 10 minutes, then turn the cakes out and cool completely on a wire rack.

Add the mascarpone to the bowl of an electric mixer. Add about 1/2 cup of the cream and beat until combined. Add the rest of the cream.

Add the powdered sugar, vanilla, and orange zest. Whip until peaks form.

Frost cake with frosting.

Add your Happy Birthday cake topper. Make a wish.