Place the water and sugar into a small saucepan and stir to combine. Place the pan on medium-high heat and stir until the sugar has dissolved. Pour the sugar water into a medium-sized bowl and whisk in the Limoncello and lemon to combine. Set the bowl aside to cool to room temperature.

Using an electric handheld or standing mixer, whip the mascarpone cheese on medium-low speed until smooth and creamy. Add the lemon curd, Limoncello, and lemon juice to the mascarpone, and mix until well combined. Transfer to another mixing bowl and set it aside.

Using a clean bowl and your electric mixer, whip the cream and sugar together until you get stiff peaks.

Add about one-third of the whipped cream to the mascarpone mixture and fold in gently with a spatula. Continue to fold the cream into the mascarpone until everything is combined.

Dip one Ladyfinger at a time into the cooled Limoncello syrup for about 2 seconds, and place into rows in a 9"x13" baking dish. Squeeze the ladyfingers together for a tight fit. Scoop half of the mascarpone and cream mixture over the ladyfingers and spread into an even layer with a spatula.
Repeat with another layer of dipped Ladyfingers and mascarpone mixture, then a final layer of ladyfingers.

Cover the Limoncello Tiramisu with plastic wrap and place in the fridge overnight, or for 8-12 hours.

To make the topping, whip the heavy cream and sugar to stiff peaks and spread over the final layer of ladyfingers. Garnish with lemon zest, lemon curls, and/or fresh mint leaves as desired. Serve and enjoy!