Lemon Buttermilk Sheet Cake

(Adapted from Cooks Country)

Cake
2 1/2 cups flour
1 teaspoon baking powder
1/2 teaspoon baking soda
1/2 teaspoon salt
3/4 cup buttermilk
3 tablespoons grated lemon zest
1/4 cup lemon juice
1 teaspoon vanilla extract
1 3/4 cup granulated sugar
12 tablespoons unsalted butter, softened
3 large eggs
1 egg yolk

Glaze
3 cups confectioners’ sugar
3 tablespoons lemon juice
2 tablespoons buttermilk

1. For the cake: preheat oven to 325 degrees. Grease and flour 13- by 9-inch baking pan. Combine flour, baking powder, baking soda, and salt in medium bowl.

2. Combine buttermilk, lemon juice, and vanilla in small bowl.

3. Beat granulated sugar and lemon zest until moist. Transfer 1/4 cup sugar mixture to small bowl, cover, and set aside. Add butter to remaining sugar mixture and beat until fluffy. Beat in eggs and yolk, just until incorporated. Add flour mixture and buttermilk mixture alternately. Mix until smooth.

4. Pour batter into prepared pan and bake until top 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.

5. For the glaze: Meanwhile, whisk confectioners’ sugar, lemon juice, and buttermilk until smooth. Gently spread glaze over warm cake and sprinkle evenly with reserved sugar mixture. Cool completely before serving.