Variation: Chocolate Olive Oil Chiffon Cake
Olive oil can be used in baking recipes, instead of vegetable oil or other liquid fats, but not in place of solid fats, such as butter or shortening. Use extra-light or extra-virgin olive oil, or even canola or grapeseed oil, because they do not impart any flavor to the recipe. 
CAKE RECIPE HELP

INGREDIENTS
2 1/2 cups sifted cake flour; sift flour into measuring cup and level to top
2 teaspoons baking powder
1/2 teaspoon salt

5 large egg whites
1 cup sugar, divided
4 large egg yolks
2 teaspoons vanilla
1 tablespoon water or orange flower water, optional
finely grated zest of 1 orange and 1 lemon

1/2 cup plus 2 tablespoons extra-light or extra-virgin olive oil
1 1/3 cups milk

INSTRUCTIONS
1. Position the oven shelf to the lower third of the oven and preheat the oven to 375 degrees F.
Oil or butter and flour a 10-inch springform pan or 10- x 4-inch Bundt pan with a removable bottom.

2. Combine the flour, baking soda and salt in a mixing bowl and set aside.

3. In a mixing bowl of a stand mixer, beat the whites until they form soft peaks; then gradually add 1/3 cup of the sugar, at the side of the bowl with the mixer running, and continue beating until stiff peaks are formed. Carefully scrape them into a large mixing bowl and set aside.

4. In the same mixing bowl of the stand mixer –don't bother to rinse it – beat the yolks with the remaining 2/3 cup sugar, until thick and light colored. Lower the speed, add the vanilla, water and citrus zests, then gradually pour in the oil. The batter will be thick, like mayonnaise.

Slowly add the milk, then whisk in the flour mixture. Reach thoroughly around the bottom of the bowl to make sure everything is well mixed.

5. Fold the in the egg whites.

6. Bake in the center of the oven for 25 minutes, then reduce the temperature to 325 degrees F.
Bake 40 minutes more or until a cake tester comes out clean and the cake has begun to pull away from the sides.

7. Let cool in the pan 10 minutes. Remove the sides of the springform pan or invert, if using a Bundt pan, onto a cooling rack. When cool, gently transfer to a cake plate and dust with powdered sugar.

VARIATIONS
CHOCOLATE CHIFFON OLIVE OIL CAKE
INGREDIENT ADJUSTMENTS
Replace 1/2 cup cake flour with Natural Cocoa Powder.
Omit finely grated zest of 1 orange and 1 lemon, if desired, but I would leave it in – I think it would taste wonderful in the chocolate version

INSTRUCTIONS
1. After measuring, sift together cake flour, cocoa powder, baking powder and salt before use.
2. Bake at 350 degrees F to start – for 25 minutes. Then, reduce oven heat to 325 degrees F.

Adapted from Deborah Madison, Vegetarian Suppers