Reprinted from Joy of Baking
I have tried a fair number of “orange” recipes in the Authentic Florida test kitchen and find that orange is a very subtle flavor. So, subtle, it is often missed. This orange chiffon cake recipe not only looks like an orange cake it tastes like one! You will have to dedicate some time to this recipe. It's a lot like making an angel food cake - but the results are well worth it. My comments are italicized.
Preheat Oven: 325 degrees
1 ungreased 10” tube pan with removable bottom
Use all room temperature ingredients (especially the wet ingredients)
In a bowl, combine:
2 ¼ cups sifted cake flour
1 ¼ cups sugar
1 Tbsp. baking powder
1 Tbsp. salt
In another bowl, beat on high speed until smooth:
5 large egg yolks
¾ cup of orange juice (I squeezed fresh orange juice for maximum flavor)
½ cup of vegetable oil
1 tsp. grated orange zest
1 tsp. vanilla
Stir into the flour mixture until smooth. In another large bowl, beat on medium speed until soft peaks form:
8 large egg whites
½ tsp cream of tartar
Gradually add, beating on high speed:
¼ c. sugar
Beat until the peaks are stiff but not dry. Use a rubber spatula to fold one-quarter of the egg whites into the egg yolk mixture, then fold in the remaining egg whites. Scrape the batter into the pan and spread evenly. Bake until the top springs back when lightly pressed and a toothpick inserted into the center comes out clean, 55-65 minutes. Let cool upside down for at least 1 ½ hours, setting the tube over a bottleneck or resting the pan on four glasses.
Quick Orange Icing
Have all your ingredients ready and watch the mixture carefully as it cooks. Melt, or heat, in the top of a double boiler on low heat.
½ stick unsalted butter (4 Tbsp.)
Remove from heat and add:
2 cups of powdered sugar (sift if lumpy)
1-2 Tbsp. Orange juice
1/8 tsp. Salt
Zest of 1 Orange
Cook, stirring occasionally over barely simmering water for 5 minutes. Remove from heat and add:
1 tsp. vanilla
Beat until cool and the desired consistency. To store, cover the surface of the icing with a sheet of plastic wrap. Pour over the cake after cooled or individual slices. I heated in a microwave for 10-20 seconds to return to a liquid state.