This light, moist sponge cake is simple to make. The subtle almond flavor complements our Stone-Fruit Trifle with Lemon Mousse nicely.
Preheat oven to 400 degrees. Arrange almonds in a single layer on a rimmed baking sheet, and toast until golden and fragrant, about 10 minutes. Transfer sheet to a wire rack, and let cool.
Reduce oven temperature to 350 degrees. Pulse almonds in a food processor until coarsely ground. Add flour and 1/2 teaspoon salt; continue to pulse until finely ground.
Butter a 9-inch round cake pan, and dust with flour, tapping out excess. Combine yolks, 1/2 cup sugar, and the vanilla in a large bowl. Whisk until pale and fluffy, about 2 minutes.
Whisk whites with a mixer on medium speed until soft peaks form. Raise speed to high, and gradually add remaining 1/4 cup sugar. Beat until stiff, glossy peaks form, about 4 minutes.
Fold egg-white mixture into yolk mixture. Working in 3 additions, fold in almond-flour mixture. Pour batter into prepared pan, and smooth top using an offset spatula.
Bake until cake is deep gold and a toothpick inserted into the center comes out clean, 30 to 35 minutes. Transfer pan to wire rack, and let cool for 30 minutes. Turn out cake from pan, and let cool completely. Halve cake crosswise, and cut each into quarters to use for trifle.