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1
Put oven rack in middle position and preheat oven to 350u00b0F. Grease springform pan with some oil, then line bottom with a round of parchment paper. Oil parchment.
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2
Finely grate enough lemon
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3
to measure 1 1/2 teaspoons and whisk together with flour. Halve lemon, then squeeze and reserve 1 1/2 tablespoons fresh lemon juice.
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4
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 lemon juice, beating until just combined (mixture may appear separated). Using a wooden spoon, stir in flour mixture (do not beat) until just combined.
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5
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.
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6
Gently fold one third of whites into yolk mixture to lighten, then fold in remaining whites gently but thoroughly.
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7
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 tablespoons sugar. Bake until puffed and golden and a wooden pick or skewer inserted in center of 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 cake to a serving plate.
