Combine limoncello, sugar, water, and a little lemon juice in a shallow dish. Dip each ladyfinger for just 1–2 seconds on each side. I like keeping them slightly crisp to prevent a soggy base.
Whip heavy cream until soft peaks form. In a separate bowl, gently fold mascarpone, lemon curd, sugar, and lemon juice together. Then carefully fold in the whipped cream to create a smooth, airy cream.
Start with a layer of dipped ladyfingers, followed by a generous layer of lemon mascarpone cream. Repeat until your dish is full, finishing with cream on top. I usually smooth the top with a spatula for a clean look.
Cover the tiramisu and refrigerate for at least 6 hours, but overnight is ideal. This allows flavors to meld beautifully and gives the dessert its signature creamy texture.