Preheat your oven to 350°F (175°C) and grease a 12x17 inch sheet pan with parchment paper.

In a medium bowl, whisk together the cake flour, baking powder, baking soda, and salt until well combined.

In a large mixing bowl, beat the unsalted butter and granulated sugar together until light and fluffy. Add the eggs, one at a time, mixing well after each addition.

Gradually add the dry flour mixture and buttermilk to the butter mixture, alternating between the two, mixing until just combined. Gently fold in the lemon juice and zest.

Pour the batter into the prepared pan and bake for 30-35 minutes, or until the edges pull away from the sides and a toothpick comes out clean.

Allow the cake to cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.

In a mixing bowl, beat the cream cheese until smooth, then gradually add the powdered sugar. Fold in the lemon juice and lemon zest to taste.

Spread the cream cheese frosting evenly over the cooled cake and garnish with additional lemon zest or slices if desired.