Lemon Buttermilk Sheet Cake

Lemon Buttermilk Sheet Cake 2 1/2 cups cake flour 1 teaspoon baking powder 1/2 teaspoon baking soda 1/2 teaspoon salt 3/4 cup buttermilk, room temperature 3 tablespoons grated zest and 1/4 cup juice from 3 lemons 1 teaspoon vanilla extract 1 3/4 cups granulated sugar 12 tablespoons (1 1/2 sticks) unsalted butter, softened 3 large eggs plus 1 egg yolk, room temperature Glaze 3 cups confectioners’ sugar 3 tablespoons lemon juice 2 tablespoons buttermilk For the cake: Adjust oven rack to middle position and preheat oven to 325 degrees. Line a 9 x 13 baking pan with foil and lightly spray with nonstick cooking spray. Combine flour, baking powder, baking soda and salt in a medium bowl. Combine buttermilk, lemon juice and vanilla in a liquid measuring cup. With electric mixer on medium speed, beat granulated sugar and lemon zest until moist and fragrant, about 1 minute. Transfer 1/4 cup sugar mixture to small bowl, cover and reserve. Add butter to remaining sugar mixture and beat until light and fluffy, about 2 minutes. Beat in eggs and yolk, one at a time, until incorporated. Reduce speed to low. Add flour mixture in 3 additions, alternating with 2 additions of buttermilk mixture, and mix until smooth, about 30 seconds. Scrape batter into prepared pan and smooth top. Bake until cake is golden brown and toothpick inserted into center comes out clean, 25 to 35 minutes. Transfer cake to wire rack and let cool 10 minutes. For the glaze: whisk confectioners’ sugar, lemon juice, and buttermilk until smooth. Gently spread glaze over warm cake and sprinkle evenly with reserved sugar mixture. Cool completely, at least 2 hours. Serve