Prepare Lemon Syrup: Combine lemon juice and sugar in a saucepan over medium-low heat for 3-5 minutes until the sugar dissolves. Stir in limoncello and lemon zest, then cool.

Make Mascarpone Cream: In a bowl, beat mascarpone until smooth. In another, whip cream with powdered sugar and vanilla until soft peaks form. Fold whipped cream into mascarpone with a pinch of salt.

Assemble Tiramisu: Dip ladyfingers quickly in the cooled syrup and arrange in a serving dish. Spread half of the mascarpone cream over the ladyfingers.

Repeat the Layers: Continue layering with dipped ladyfingers, then spread remaining mascarpone cream on top.

Chill: Cover and refrigerate for at least 4 hours or overnight.

Serve: Garnish with lemon zest and mint leaves, cut into squares and serve chilled.