Because there is no butter in the sponge cake, it will remain soft when frozen in the Lemon Semifreddo Cake.

　　

Ingredients

Makes one 9 x 13-inch sheet cake

　　1 cup all-purpose flour

　　Pinch of salt

　　1/2 teaspoon baking powder

　　4 large eggs, separated

　　1 cup sugar

　　3 tablespoons boiling water

　　1 vanilla bean, split and scraped

　　

Step 1

Preheat the oven to 350°F. Line a 9 × 13-inch baking pan with parchment paper, and set aside. Sift together the flour, salt, and baking powder in a medium bowl.

　　

Step 2

In the bowl of an electric mixer fitted with the whisk attachment, beat together the egg yolks and sugar on medium-low speed until light and fluffy. Beat in the water and vanilla bean scrapings. Add the dry ingredients in 3 batches, scraping down the sides of the bowl with a rubber spatula as needed, just until the flour mixture is incorporated after each addition.

　　

Step 3

In another mixing bowl, beat the egg whites until stiff but not until dry peaks form; whisk one-quarter of the egg whites into the batter to lighten. Fold in the remaining egg whites, and pour the batter into the prepared pan. Bake until the cake springs back when gently pressed in the center, 15 to 20 minutes. Transfer to a wire rack to cool completely.

　　Reprinted with permission from The Martha Stewart Living Cookbook: The New Classics by Martha Stewart Living Magazine, copyright © 2007. Published by Clarkson Potter, a division of The Crown Publishing Group.Buy the full book from Amazon.