Preheat the oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.

In a mixing bowl, cream together the softened butter and granulated sugar until light and fluffy.

Add the eggs one at a time, mixing well after each addition.

In another bowl, whisk together the flour, baking powder, baking soda, and salt.

Gradually add the dry ingredients to the butter mixture, alternating with the buttermilk. Mix until just combined.

Stir in the lemon zest and vanilla extract.

Divide the batter evenly between the prepared cake pans.

Bake for 25-30 minutes or until a toothpick inserted into the center comes out clean.

Allow the cakes to cool in the pans for 10 minutes, then transfer to a cooling rack to cool completely.

In a mixing bowl, beat the softened butter until creamy.

Gradually add the powdered sugar, mixing on low speed until combined.

Add the lemon juice and lemon zest, mixing until smooth and creamy.

If the frosting is too thick, add milk a tablespoon at a time until desired consistency is reached.

Once the cakes are completely cool, place one layer on a serving plate.

Spread a layer of frosting on top of the first cake layer.

Place the second cake layer on top and frost the top and sides of the cake.

Decorate as desired and serve.