Place oven rack in middle position and preheat oven to 350°F. Grease springform pan with olive oil
Finely zest 1 1/2 teaspoons of lemon and whisk together with the flour. Halve the lemon, then squeeze and reserve 1 1/2 tablespoons fresh lemon juice.
Using the paddle attachment, in a large bowl beat together yolks and 1/2 cup sugar at high speed until thick and very pale yellow, 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 or rubber spatula, stir in flour mixture (do not beat) until just combined.
Using the whisk attachment, in a clean large bowl beat egg whites with 1/2 teaspoon salt at medium-high speed until foamy, then add 1/4 cup sugar in a slow pour, 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 the base, then fold in remaining whites gently but thoroughly.
Transfer batter to springform pan. 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 hour. Can be made 1-2 days ahead, completely cooled, and wrapped well in plastic wrap.
To make the garnish, in a medium bowl stir together the crème fraiche and lemon curd. Place a dollop on top of each slice of cake when serving and top with fresh berries. For dinner parties, you can serve the whole cake on a slightly rimmed cake stand or cake plate.
Note: Adapted from a 2006 Gourmet magazine recipe.