In a medium saucepan, combine fresh lemon juice, water, and granulated sugar over medium heat. Stir continuously until the sugar dissolves completely, about 3-5 minutes.

Remove the pan from heat and allow the syrup to cool completely.

Chill a mixing bowl and beaters in the freezer for 10 minutes. Whip the cold heavy whipping cream with powdered sugar and pure vanilla extract until soft peaks form, about 3-5 minutes.

In a separate bowl, beat the mascarpone cheese with lemon zest until fluffy. Gently fold the whipped cream into the mascarpone mixture.

Prepare a 9x9 inch dish for layering your Lemon Tiramisu. Briefly dip each ladyfinger into the cooled lemon syrup for 1-2 seconds.

Layer the dipped ladyfingers evenly in the dish, then spread half of the mascarpone cream mixture over them.

Repeat this process with another layer of soaked ladyfingers and the remaining mascarpone cream on top.

Cover the completed Lemon Tiramisu with plastic wrap and refrigerate for a minimum of 4-6 hours.

Before serving, sprinkle fresh lemon zest on top and garnish with mint leaves or candied lemon slices.

Slice into squares and serve chilled.