In a mixing bowl, whisk together the mascarpone cheese, heavy cream, powdered sugar, vanilla extract, and lemon zest until smooth and creamy.

In a small saucepan, combine the limoncello, water, and sugar. Heat gently until the sugar dissolves, then remove from heat and let cool.

Quickly dip each ladyfinger into the limoncello soak, ensuring they are soaked but not soggy. Layer half of the soaked ladyfingers in the bottom of a 9x9 inch baking dish.

Spread half of the cream mixture over the ladyfingers. Repeat with another layer of soaked ladyfingers and the remaining cream mixture.

Cover the dish with plastic wrap and refrigerate for at least 4 hours, preferably overnight, to allow the flavors to meld.

Before serving, dust the top with powdered sugar and garnish with lemon zest.