In a small saucepan, combine the fresh lemon juice, water, and granulated sugar. Heat over medium heat, stirring constantly until the sugar has fully dissolved, about 3-4 minutes. Remove from heat and let cool completely.

In a large mixing bowl, whip the cold heavy cream, powdered sugar, and vanilla extract until soft peaks form, about 4-5 minutes. In another bowl, gently beat the mascarpone cheese with lemon zest until smooth. Fold the whipped cream into the mascarpone mixture until fluffy.

Briefly dip each ladyfinger into the cooled lemon syrup for 1-2 seconds. Arrange half of the soaked ladyfingers in a single layer at the bottom of the dish. Spread half of the mascarpone cream mixture over the ladyfingers.

Repeat the layering with the remaining ladyfingers and mascarpone cream, ensuring a smooth finish on top.

Cover tightly with plastic wrap or a lid and refrigerate for at least 4-6 hours, preferably overnight.

Just before serving, garnish with extra lemon zest or candied lemon slices. Scoop into servings and enjoy.