3/4 cup olive oil, plus additional for greasing pan
1 large lemon
1 cup cake flour
5 large eggs, separated, reserving 1 white for another use
3/4 cup plus 1 1/2 T sugar
Preheat oven to 350 degrees. Grease 9" springform pan with olive oil, then line bottom with a round of parchment paper. Oil parchment.
Finely grate enough lemon zest to measure 1 1/2 teaspoons and whisk together with flour. Squeeze 1 1/2 T lemon juice and set aside in a prep bowl.
Beat together egg 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, and reserved lemon juice, beating until just combined. Using a wooden spoon, stir in flour mixture (do not beat) until just combined.
Beat egg whites from 4 eggs with 1/2 teaspoon salt in another large bowl at medium-high speed until foamy (make sure beaters are clean) , 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. Sprinkle top evenly with remaining 1 1/2 T sugar. Bake until puffed and golden and a wooden pick inserted in center comes out clean, about 45 minutes.
Cool cake in pan on a rack for 10 minutes, then run a thin knife around the edge of the pan and remove sides. Cool cake to room temp and remove bottom of pan and peel off parchment. Transfer cake to a serving plate.