- Unsalted butter, for pans
- 3/4 cup all-purpose flour, plus more for pans
- 3/4 cup cornstarch
- 6 large eggs, separated
- 1 1/2 teaspoons pure vanilla extract
- 3/4 cup plus 6 tablespoons sugar
- 1/4 teaspoon table salt
- Preheat the oven to 350 degrees. Butter the bottom and sides of an 11-by-17-inch rimmed baking sheet and a 9-inch-diameter round cake pan. Line the bottom of each pan with parchment paper, and butter again. Flour the pans, and set aside. In a small bowl, sift together the flour and cornstarch; set aside.
- In the bowl of an electric mixer fitted with the whisk attachment, beat egg yolks, vanilla, and 3/4 cup sugar on high until thick and pale, about 3 minutes. Transfer egg-yolk mixture to a large bowl. Wash and dry the mixer bowl and the whisk attachment.
- Combine the egg whites and salt in the mixer bowl, and beat on medium speed until soft peaks form, about 1 1/2 minutes. With the mixer running, slowly add the remaining 6 tablespoons sugar. Continue beating until stiff and glossy, about 1 minute.
- Fold the egg-white mixture into the egg-yolk mixture. In three additions, fold the reserved flour mixture into the egg mixture. Transfer two-thirds of the batter to the baking sheet, and smooth the top with an offset spatula. Transfer remaining batter to the round cake pan; smooth the top with the spatula. Bake until light golden brown and a cake tester inserted into the center comes out clean, about 20 minutes. Transfer the pans to wire racks to cool; turn out the cakes, remove the parchment paper, and wrap in plastic wrap until ready to use.
The cakes can be made ahead, cooled completely, and frozen for up to 2 weeks. Thaw completely at room temperature before using.