Toasting the almonds gives this sponge cake a golden color and a nuttier flavor.
Preheat oven to 400 degrees. Place almonds in a single layer on a rimmed baking sheet; toast until golden, about 10 minutes. Transfer pan to a wire rack, and let almonds cool.
Reduce oven temperature to 350 degrees. Place the cooled almonds and the cornstarch in bowl of a food processor. Process until finely ground, about 30 seconds. Set aside.
Butter two 6-inch-round layer-cake pans. Line pans with parchment paper, and butter again. Flour pans, and set aside.
In the bowl of an electric mixer fitted with the whisk attachment, mix together egg yolks and vanilla. With mixer on high speed, gradually add 1/4 cup sugar. Beat until pale, thick, and light, about 5 minutes. Transfer egg-yolk mixture to a large bowl; set aside. Wash and dry mixer bowl and attachment.
Place egg whites and salt in the clean mixer bowl. Beat on medium speed until soft peaks form. Increase the speed to high, and gradually add the remaining sugar. Beat until stiff and glossy, about 4 minutes.
Fold the egg-white mixture into the egg-yolk mixture. In three additions, fold the reserved ground-almond mixture into this new mixture. Divide the batter between the two prepared pans, and smooth the tops with an offset spatula.
Bake cakes until a cake tester inserted into the middle comes out clean, 25 to 30 minutes. Transfer pans to a wire rack to cool, about 25 minutes. Turn out cakes, and cover with plastic wrap until ready to use.