(From Everyday Food Magazine, May 2009, pp. 116-118)
1/2 teaspoon baking soda
1 teaspoon salt
1 1/2 cups sugar
1 cup (2 sticks) unsalted butter, room temperature, plus more for pans
2 large eggs plus 3 large egg yolks (reserve egg whites for frosting)
2 tablespoons fresh lemon juice
1 cup low-fat buttermilk
1. Preheat oven to 350°. Butter and flour two 8-by-2-inch cake pans, tapping out excess flour. In a medium bowl, whisk four, baking powder, baking soda, salt (half amount of salt if using salted butter), and lemon zest.
2. In a large bowl, using an electric mixer, beat butter and sugar until light and fluffy. With mixer on low, beat in eggs and yolks, one at a time. Beat in fresh lemon juice. Alternately beat in flour mixture and buttermilk, beginning and ending with flour mixture; mix just until combined.
3. Divide batter between pans; smooth tops. Bake until cakes pull away from sides of pans, 32 to 35 minutes. Let cool in pans 10 minutes. Run a knife around edges of pans and invert cakes onto a wire rack.
4. While cakes are baking, bring 1/2 cup sugar and 1/2 cup water to a boil in a saucepan. Add 1 thinly sliced and seeded lemon and simmer 25 minutes. Using a slotted spoon, transfer lemon slices to a waxed-paper-lined plate. Stir 1/4 cup fresh lemon juice into syrup.
5. Using a toothpick, poke holes in warm cakes on rack. Brush with lemon syrup. Let cakes cool completely.
6. Place one cake, bottom side up, on a cake stand. Tuck strips of parchment paper underneath. Using an offset-spatula or table knife, spread top with Whipped Frosting. Top with remaining cake; frost top, then sides. Top with candied lemon slices.
In a heatproof bowl set over (not in) a saucepan of simmering water, combine 3 large egg whites, 3/4 cup sugar, a pinch salt, and 1/3 cup water. Cook over medium, stirring constantly, until sugar has dissolved (or mixture registers 150° on an instant-read thermometer), 2 to 3 minutes. Transfer to a large bowl. Using an electric mixer, beat on medium-high until glossy, stiff peaks form (do not overbeat), about 3 minutes; reduce speed to low, add 2 tablespoons fresh lemon juice, and beat just until combined. Use immediately. Makes 5 cups.