Step 1

Preheat oven to 350°F. Prepare a 9 in. square pan with vegetable cooking spray.

Step 2

In a medium bowl, whisk together flour, baking powder, salt and baking soda.

Step 3

In a large bowl, beat sugar, butter and lemon zest with an electric mixer on medium speed until light and fluffy, about 3-5 minutes.

Step 4

Add eggs, one at a time, beating well.

Step 5

Scrape down bottom and sides of bowl and beat in lemon juice and vanilla.

Step 6

Add flour mixture alternately with sour cream, beginning and ending with flour. Do not overmix.

Step 7

Pour batter into prepared pan and spread into an even layer. Bake 38-45 minutes or until toothpick inserted in center of cake comes out clean. Cool in pan on cooling grid 10 minutes, then remove cake to cooling grid, or cool completely in pan on cooling grid.

Step 8

Beat butter with mixer on medium speed until smooth.

Step 9

Add 1 cup of confectioners’ sugar at a time and beat until smooth. Frosting will appear dry.

Step 10

Add lemon juice and zest; beat until light and fluffy. Spread onto cooled cake.