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

In a large mixing bowl, whip heavy whipping cream with powdered sugar and vanilla extract until soft peaks form, approximately 3-5 minutes. In another bowl, mix mascarpone cheese with lemon zest until creamy. Gently fold whipped cream into mascarpone until well combined.

Dip ladyfinger cookies briefly in cooled lemon syrup, ensuring they're lightly coated. Arrange a layer in a 9x9-inch dish. Spread half of the mascarpone cream mixture on top. Repeat with another layer of ladyfingers and the remaining mascarpone cream.

Cover the dish with plastic wrap and chill for at least 4-6 hours, ideally overnight.

When ready to serve, uncover the dessert, garnish with lemon zest or candied lemon slices, cut into squares, and enjoy!