In a medium saucepan, combine 1 cup of freshly squeezed lemon juice, ½ cup of water, and ½ cup of granulated sugar over medium heat. Stir until the sugar has fully dissolved and the liquid begins to simmer, about 3-5 minutes. Remove from heat and allow to cool completely.

In a large mixing bowl, whip 1 cup of cold heavy cream with ⅓ cup of powdered sugar and 1 teaspoon of vanilla extract using an electric mixer on medium speed until soft peaks form, about 4-5 minutes. In a separate bowl, beat 1 cup of mascarpone cheese with 1 tablespoon of lemon zest until smooth. Gently fold the whipped cream into the mascarpone mixture.

Quickly dip 24 ladyfinger cookies in the cooled lemon syrup for 1-2 seconds. Arrange a layer of ladyfingers in a 9x9-inch dish. Spoon half of the lemon mascarpone cream over the ladyfingers. Repeat with another layer of ladyfingers and remaining mascarpone cream.

Cover with plastic wrap or a lid and refrigerate for 4-6 hours, preferably overnight.

Before serving, garnish with additional lemon zest, mint leaves, or candied lemon slices. Cut into squares and serve.