In a small saucepan, combine lemon juice, water, and sugar. Heat until sugar dissolves, about 2-3 minutes. Cool completely.

In a mixing bowl, whip heavy cream, powdered sugar, and vanilla until soft peaks form, about 3-4 minutes. In another bowl, mix mascarpone and lemon zest until smooth. Fold in whipped cream.

Dip ladyfingers into cooled syrup briefly and layer in dish. Spread half of the mascarpone mixture over ladyfingers. Repeat layers.

Cover and chill in the refrigerator for at least 4-6 hours or overnight.

Before serving, garnish with lemon zest or mint, cut into squares, and serve chilled.