In a medium saucepan, combine fresh lemon juice, water, and granulated sugar over medium heat. Stir until sugar dissolves completely, about 3-5 minutes. Remove from heat and let cool.

In a large mixing bowl, whip together cold heavy whipping cream, powdered sugar, and vanilla extract until soft peaks form, about 3-5 minutes. In another bowl, beat mascarpone cheese and lemon zest until smooth. Fold in whipped cream gently.

Dip each ladyfinger briefly in the cooled lemon syrup for 1-2 seconds. Layer half in a 9x9-inch dish, spread half of the mascarpone cream mixture on top, and repeat with remaining ladyfingers and cream.

Cover and refrigerate for at least 4-6 hours, overnight if possible, to allow flavors to meld and the texture to set.

Before serving, garnish with fresh lemon zest, mint leaves, or candied lemon slices for presentation and extra flavor.