This recipe is used in our Passion Fruit and Lime Cake.
Preheat oven to 350 degrees. Spray bottom and sides of two 9-inch-round-by-2-inch-high pans with vegetable oil spray; line bottom of each pan with parchment paper, spray again, then dust each pan with flour, knocking out excess; set aside.
In small bowl, sift together 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 mixer bowl and whisk attachment.
Combine egg whites and salt in the mixer bowl, and beat on medium speed until soft peaks form, about 1 1/2 minutes. With mixer running, slowly add remaining 6 tablespoons sugar. Continue beating until stiff and glossy, about 1 minute.
Fold egg-white mixture into egg-yolk mixture. In three additions, fold reserved flour mixture into egg mixture. Equally divide batter between cake pans and smooth tops with a spatula. Bake until light golden brown and until a toothpick inserted into the centers comes out clean, 20 to 30 minutes. Transfer pans to wire racks to cool; turn out cakes, remove 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.