In a large bowl or the bowl of a stand mixer, mix the mascarpone cheese on medium-low speed until it's loosened up, about 30 seconds.
Add the lemon curd and mix until combined. Add the limoncello and the lemon juice and mix until combined. Be careful not to overbeat the mascarpone. Set aside.
In a separate large bowl or bowl of a stand mixer, beat the heavy whipping cream and sugar until stiff peaks form.
Take about ⅓ of the whipped cream and stir it into the mascarpone mixture. Carefully fold in the rest of the whipped cream until combined.
With one ladyfinger at a time, dip into the syrup on one side for about 2 seconds and then the other side for about 2 seconds. You don't want to overly saturate the ladyfingers or the tiramisu will be too soggy. The cookie should still have a slight crispness to it after dipping.
Arrange each ladyfinger in a 9x13 pan, all facing the same direction in a single layer. Cut ladyfingers to fit as needed.
Spread half of the mascarpone cream over the first layer of ladyfingers and smooth the top. Dip the remaining ladyfingers, one at a time, and arrange them in the same way over the cream. Spread the remaining mascarpone cream over the top layer of ladyfingers and smooth the top.
Cover the dish with plastic wrap or foil and let refrigerate overnight. Top with additional whipped cream (if desired) just before serving.