Lemon Buttermilk Sheet Cake

Lemon Buttermilk Sheet Cake For the 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 lemon zest from 3 lemons 1/4 cup lemon juice from 3 lemons 1 teaspoon vanilla extract 1 3/4 cup granulated sugar 12 tablespoons (1 1/2 sticks) unsalted butter, softened 3 large eggs, room temperature 1 egg yolk, room temperature For the Glaze: 3 cups confectioners' sugar 3 tablespoons lemon juice 2 tablespoons buttermilk Preheat the oven to 325°. Grease a 9x13 inch square baking pan and set aside. In a medium bowl, whisk together the flour, baking powder, baking soda, and salt; set aside. Combine buttermilk, lemon juice, and vanilla in liquid measuring cup. In the bowl of a stand mixer beat granulated sugar and lemon zest until moist and fragrant, about 1 minute. Transfer 1/4 cup of the sugar mixture to small bowl, cover, and set aside. Add butter to the remaining sugar mixture and beat until light and fluffy, about 2 minutes. Beat in eggs and yolk, one at a time, until combined. Reduce speed to low. Add flour mixture in 3 additions, alternating with 2 additions of buttermilk mixture, and mix until smooth, about 30 seconds. Pour batter into prepared pan and smooth top with an offset spatula. Bake until cake is golden brown and toothpick inserted into center comes out with a few moist crumbs attached, 25 to 35 minutes. Transfer cake to wire rack and let cool 10 minutes. To Make the glaze: In a medium bowl whisk confectioners’ sugar, lemon juice, and buttermilk until smooth. Using an offset spatula, spread glaze over warm cake and sprinkle evenly with the reserved sugar mixture. Cool completely, at least 2 hours.