3/4 Cup Citrus Olive Oil (Eureka Lemon, Blood Orange, Persian Lime)
1 large orange
1 Cup cake flour
5 large eggs, separated, reserving 1 egg white for another use
3/4 cup plus 1 1/2 tablespoons sugar
Put oven rack in middle position and preheat to 350 degrees. Grease your pan (springform pan works best) with a little oil and line bottom with parchment paper. Oil parchment as well.
Using orange, finely grate 1 1/2 teaspoons of zest. Whisk zest with flour. Halve orange and squeeze, reserving 1 1/2 tablespoons fresh juice.
Beat together yolks and 1/2 cup sugar in a large bowl with an electric mixer at high speed until thick and pale, about 3 minutes. Reduce speed to medium and add olive oil (3/4 Cup) and reserved juice, beating until just combined (mixture may look separated). Using a wooden spoon, stir in flour mixture (don’t beat or over stir)
Beat egg whites (from 4 eggs) with 1/2 teaspoon salt in another large bowl with cleaned beaters at medium-high speed until foamy, then add 1/4 cup sugar a little at a time, beating, and continue to beat until egg whites just hold soft peaks, about 3 minutes.
Gently fold one third of whites into yolk mixture to lighten, then fold in remaining whites gently but thoroughly. Transfer batter to springform pan and gently rap against work surface once or twice to release any air bubbles. Sprink top evenly with remaining 1 1/2 tablespoons sugar. Bake until puffed and golden and wooden pick or skewer inserted in centor cake comes out clean, about 45 minutes. Cool cake in pan on a rack 10 minutes, then run a thin knife around edge of pan and remove side of pan. Cool cake to room temperature about 1 1/4 hours Remove bottom of pan and peel off parchment, then transfer to a serving plate.
Glaze with a powdered sugar-orange juice mixture.