Preheat the oven to 350°F (175°C). Grease and flour the cake pans.

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

In another bowl, cream the butter until light and fluffy. Add eggs, buttermilk, limoncello, and vanilla, mixing well.

Gradually add the dry ingredients to the wet ingredients, mixing until just combined.

Divide the batter evenly between the prepared pans and smooth the tops.

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

Let the cakes cool in the pans for 10 minutes, then transfer to wire racks to cool completely.

In a mixing bowl, beat the mascarpone cheese until smooth.

In another bowl, whip the heavy cream and powdered sugar until soft peaks form.

Gently fold the whipped cream into the mascarpone, then add limoncello and lemon zest.

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

Spread half of the mascarpone filling over the first layer.

Top with the second layer of cake and spread the remaining filling on top.

In a small bowl, mix powdered sugar, lemon juice, and lemon zest for the topping. Drizzle over the cake.

Chill the cake in the refrigerator for at least 1 hour before serving.