In a medium saucepan, combine lemon juice, water, and granulated sugar over medium heat. Stir until sugar is dissolved, about 3-5 minutes. Remove from heat to cool.

In a large mixing bowl, whip cold heavy cream with powdered sugar and vanilla until soft peaks form, about 3-4 minutes.

In another bowl, beat mascarpone with lemon zest until smooth. Gently fold in whipped cream to keep it airy.

Dip ladyfinger cookies in the cooled lemon syrup for 1-2 seconds, then arrange in a serving dish. Spread half of the mascarpone mixture over.

Repeat the layering with remaining ladyfingers and mascarpone cream.

Cover and refrigerate for 4-6 hours or overnight. Allow flavors to meld.

Garnish with lemon zest or candied lemon slices before serving. Slice and enjoy!