Make the Limoncello Syrup:In a small pan, combine 1 ⅜ cup granulated sugar, 2 ⅔ tbsp lemon zest, and 1¼ cup lemon juice. Stir the mixture over medium heat until it comes to a boil. Once boiling, remove from heat and stir in ⅖ cup Limoncello liqueur. Set aside to cool.
Prepare the Limoncello Mascarpone:In a large mixing bowl, beat together 2 ⅔ cups mascarpone cheese, 2 ¾ tbsp lemon zest, 3 ⅓ tbsp lemon juice, and 3 ⅓ tbsp Limoncello liqueur using an electric mixer until smooth and creamy. In another bowl, whip 2 ⅓ cups heavy cream until soft peaks form. Gently fold the whipped cream into the mascarpone mixture until well combined, ensuring that the texture remains light and airy.
Assemble the Tiramisu:Dip each ladyfinger cookie into the cooled Limoncello syrup briefly, making sure not to soak them too long. Layer the dipped ladyfingers on the bottom of a rectangular or square dish, forming a base layer. Spread half of the Limoncello mascarpone mixture over the ladyfingers, followed by half of the 1⅕ cup lemon curd. Repeat this layering process, finishing with the mascarpone mixture on top. If desired, add more mascarpone around the edges for a refined look.
Chill:Cover the dish with plastic wrap and refrigerate for at least 4 hours, allowing the flavors to meld together and the dessert to set. For best results, chilling overnight is recommended.