Put a delightful twist on classic sponge cake by tinting it a sweet pink hue. Serve this dessert with macerated berries and sweetened sour cream. Martha made this recipe on episode 612 of Martha Bakes.
Preheat the oven to 350 degrees. Use a fine-mesh sieve to sift together flour and 3/4 cup superfine sugar 4 times.
In the bowl of a standing mixer fitted with a whisk attachment, beat together egg whites, water, food coloring, and 3/4 cup sugar on medium speed until foamy. Add salt, cream of tartar, and 2 teaspoons vanilla; whisk until meringue is stiff but not dry.
Transfer meringue to a large bowl. In six additions, sift flour mixture on top, folding in quickly but gently.
Transfer batter to an ungreased 10-inch tube pan with removable bottom. Smooth top with an offset spatula. Run a knife through batter to release air bubbles. Bake until golden brown and springy to the touch, 35 to 40 minutes.
Invert pan on its legs or over the neck of a glass bottle, and let cool completely, about 1 hour.
Meanwhile, combine the berries, lemon juice, and remaining 1/4 cup superfine sugar in a small nonreactive bowl. Set aside to macerate while the cake is cooling, about 1 hour. In a separate bowl, stir together the sour cream, confectioners' sugar, and remaining 1 teaspoon vanilla.
Carefully run a long offset spatula or knife around the inner and outer perimeter of the pan to release cake. Invert onto serving platter. Serve with macerated berries and sweetened sour cream.