Make the syrup by melting together the sugar and water in a small sauce pan. Bring to a boil over medium heat and then add in the limoncello and lemon juice. Set aside to cool.
Mix together the mascarpone and lemon curd. Add limoncello and lemon juice. Set aside and whip whipped cream in another bowl. Fold the whipped cream into the mascarpone mixture.
Dip ladyfingers in the syrup mixture and place in a 9x13 baking dish. Do a full layer of these. Spread filling on top. Repeat layers until all is used. Cover with plastic wrap and chill for 4+ hours.