In a medium saucepan, combine 1 cup of water, 3/4 cup of granulated sugar, 1/2 cup of limoncello, and 1/4 cup of fresh lemon juice. Heat over medium-high until the sugar fully dissolves, about 3–5 minutes. Once dissolved, remove from the heat and let it cool to room temperature.

In a mixing bowl, take 1 cup of chilled mascarpone cheese and beat it gently with a spatula for about 30 seconds until it becomes loose and creamy. Mix in 1/2 cup of prepared lemon curd, 2 tablespoons of limoncello, and 2 tablespoons of lemon juice until just combined.

In a separate mixing bowl, pour in 1 cup of heavy whipping cream and 2 tablespoons of granulated sugar. Beat the mixture on medium-high speed until stiff peaks form, about 2–4 minutes.

Gently stir about one-third of the whipped cream into the mascarpone mixture to lighten it. Once combined, carefully fold in the remaining whipped cream until just incorporated.

Take 24 ladyfinger cookies and briefly dip each one into the syrup for 1–2 seconds on each side. This ensures the ladyfingers absorb the delicious lemon essence.

In a 9x13 inch baking dish, arrange the soaked ladyfingers snugly in a single layer. Spread half of the creamy mascarpone mixture over the ladyfingers, then repeat with another layer of ladyfingers and the remaining mascarpone cream on top.

Cover the assembled tiramisu and refrigerate for at least 4 hours, preferably overnight to allow the flavors to meld and the dessert to set.

For an optional topping, whip an additional cup of heavy cream with 2 tablespoons of powdered sugar until stiff peaks form. Pipe or spread this whipped cream on top and garnish with fresh lemon zest before serving.