Separate the egg whites and yolks.
Whisk egg yolks and sugar together.
Add mascarpone cheese and lemon juice to yolks.
Whip the heavy cream until soft peaks form.
Fold the whipped cream into the mascarpone mixture.
In a separate bowl, beat the egg whites to stiff peaks.
Combine the egg whites with the creamy mixture.
Dip ladyfingers in limoncello or lemon juice and layer them.
Layer the ladyfingers and cream mixture.
Chill for at least 4 hours or overnight.
Serve and garnish with lemon zest.