Prepare the syrup for the ladyfingers by placing 250 ml water with the Limoncello in a saucepan over medium heat. Add 5 tablespoons (60 grams) sugar, and mix everything well with a spoon until the sugar has completely dissolved. Remove from heat, and reserve.

Separate the egg yolks from the egg whites into two medium bowls. Using a hand mixer, beat the egg whites on high speed until stiff peaks form.

To egg yolks, add remaining ½ cup plus 1½ tablespoons (120 grams) sugar, and beat with hand mixer on high speed until pale and thick, about 1 minute. Add mascarpone, lemon zest, and juice, and beat on medium until well combined. Add yolk mixture to stiff egg whites, and using a whisk, fold the ingredients together, folding from the bottom up to avoid deflating the egg whites.

Soak the ladyfingers in lemon syrup for a few moments, one at a time. Start arranging the ladyfingers on the bottom of a 10x7.5-inch (25x19cm) baking dish as you soak them in the syrup. Form a layer of ladyfingers and then cover them with a layer of mascarpone and lemon cream (about 2½ cups/420 grams). Repeat the operation with a second layer of ladyfingers and then with a second layer of cream.

Top with whipped cream as desired. Sprinkle the surface of the lemon tiramisù with a dusting of grated lemon zest and then the dessert will be ready to be served at the table, after having rested for at least an hour in the refrigerator