Preheat your oven to 350°F (175°C) and prepare two 9-inch round cake pans with parchment paper and butter.

Cream together 1 cup of butter with 2 cups of sugar until light and fluffy, then add 4 eggs and 2 yolks one at a time, along with 2 tablespoons of lemon zest and 1/3 cup of lemon juice.

In a separate bowl, whisk together 3 cups of flour, 1 teaspoon baking powder, 1/2 teaspoon baking soda, and 1/2 teaspoon salt.

Alternately add the dry ingredients and 1 cup of sour cream mixed with 1 cup of milk to the butter mixture.

Divide the batter into the prepared pans and bake for 24-28 minutes. Let cool for 10 minutes before transferring to wire racks.

Make the syrup by boiling 1/2 cup sugar and 1/2 cup lemon juice until it thickens.

Beat 8 ounces of cream cheese with 1/2 cup butter, then gradually add 4 cups confectioners' sugar and 1 tablespoon lemon juice until creamy.

Slice each cooled cake layer horizontally into two layers, brush with warm lemon syrup, then assemble with cream cheese frosting between layers.

Spread frosting on the top and sides of the assembled cake, then decorate as desired and let sit before serving.