In a medium saucepan, combine 1 cup of water and ½ cup of granulated sugar over medium-high heat. Stir continuously until the sugar dissolves, about 3-5 minutes. Remove from heat and stir in ½ cup of limoncello and ¼ cup of fresh lemon juice. Set aside to cool.

In a large mixing bowl, beat 1 cup of mascarpone cheese on low speed for about 30 seconds until slightly loose. Slowly add in ½ cup of prepared lemon curd, 2 tablespoons of limoncello, and 2 tablespoons of fresh lemon juice, mixing gently until just combined.

In a separate chilled bowl, whip 1 cup of heavy cream with 2 tablespoons of powdered sugar until stiff peaks form, about 3-5 minutes. Gently fold one-third of the whipped cream into the mascarpone mixture, then fold in the remaining whipped cream.

Dip each ladyfinger briefly into the cooled limoncello syrup, ensuring they are soaked but not soggy. Arrange a layer of the dipped ladyfingers in a 9x13-inch baking dish. Spread half of the mascarpone mixture over the ladyfingers and repeat with the remaining ladyfingers and mascarpone.

Cover with plastic wrap and refrigerate for at least 4 hours, preferably overnight, to let the flavors meld and layers set.

Remove from the refrigerator and top with whipped cream and a sprinkle of lemon zest before serving. Slice into squares.