In a medium saucepan, combine freshly squeezed lemon juice, water, and granulated sugar. Heat over medium flame, stirring gently until the sugar fully dissolves—approximately 3-5 minutes. Allow the syrup to cool completely at room temperature.

In a large mixing bowl, whip the cold heavy whipping cream on medium speed until soft peaks form, about 4-5 minutes. Add powdered sugar and pure vanilla extract, continuing to whip until stiff peaks form.

In a separate bowl, combine mascarpone cheese and lemon zest. Beat until smooth, then gently fold in the whipped cream mixture.

Dip each ladyfinger into the cooled lemon syrup for 1-2 seconds. Arrange a single layer in a 9x13 inch dish, spread half of the mascarpone cream over, then repeat with another layer.

Cover and refrigerate for at least 4-6 hours or overnight to set.

Before serving, garnish with extra lemon zest or mint leaves, slice into squares and serve chilled.