This tender, moist sponge cake can be used in place of the drier, comparatively coarse-textured génoise. It also makes a perfectly flexible sponge sheet, for jelly rolls.
Have all ingredients at room temperature, 68┬░ to 70┬░F. Preheat the oven to 350┬░F. Grease and flour the bottom of one 9 x 2-inch round pan or line the bottom with wax or parchment paper.
Sift together 3 times and return to the sifter:
3/4 cup sifted cake flour
1 teaspoon baking powder
Heat in a small saucepan until the butter is melted:
1/4 cup milk
2 tablespoons unsalted butter
In a large bowl, beat until light-colored, tripled in volume, and the consistency of softly whipped cream (3 to 4 minutes in a heavy-duty mixer with the whisk attachment, 10 to 15 minutes with a hand-held mixer):
3/4 cup sugar
5 large eggs
Reheat the butter and milk until steaming hot. In 3 additions, sift the flour mixture over the top of the egg mixture and fold in. Add the hot milk mixture all at once and fold in until well combined. Scrape the batter into the pan and spread evenly. Bake until the top springs back when lightly pressed and a toothpick inserted into the center comes out clean, 20 to 25 minutes. Let cool in the pan on a rack for 10 minutes. Slide a thin knife around the cake to detach it from the pan. Invert the cake and peel off the paper liner, if using. Let cool right side up on the rack.
