Begin by combining 1 cup of water and 1 cup of granulated sugar in a medium saucepan. Heat the mixture over medium heat, stirring gently until the sugar completely dissolves, about 5 minutes. Once dissolved, remove the saucepan from heat and stir in 1 cup of limoncello and ½ cup of lemon juice. Allow the syrup to cool to room temperature.

In a large mixing bowl, beat 16 ounces of mascarpone cheese until it's loosened and smooth, taking about 2 minutes with a hand mixer. Next, mix in ½ cup of prepared lemon curd, 2 tablespoons of limoncello, and 2 tablespoons of lemon juice until combined. Gently fold in 1 cup of heavy whipping cream that has been whipped to soft peaks for a light, airy texture.

Quickly dip ladyfinger cookies, about 24 pieces, into the cooled limoncello syrup for about 2 seconds per side to achieve just the right saturation. Arrange a layer of these soaked ladyfingers in the bottom of a 9x13 inch pan. Spread half of the mascarpone cream mixture generously over the ladyfingers, using a spatula to ensure even coverage.

Add another layer of soaked ladyfingers on top of the first cream layer in the 9x13 inch pan, repeating the dipping process as before. Follow with the remaining mascarpone cream, smoothing it out with your spatula to create a beautiful top layer for your Limoncello Tiramisu.

Cover the dish tightly with plastic wrap or aluminum foil and place it in the refrigerator. Allow the Limoncello Tiramisu to chill for at least 4 hours, or overnight if possible, to let the flavors meld and the dessert set perfectly.

Just before serving, whip an additional cup of heavy cream with 2 tablespoons of powdered sugar until soft peaks form. Pipe dollops of this sweetened whipped cream over the top of the Limoncello Tiramisu for an elegant finish. Lastly, sprinkle some lemon zest on top for an added burst of flavor and visual appeal.