Gather Ingredients.

For Lemon Curd: Combine lemon juice, 2 cups white sugar, eggs, egg yolks, and salt in a large non-reactive saucepan.

Cook, stirring constantly, over medium until mixture thickens and starts to bubble. Cook over medium-low heat for 2 minutes more. Remove from heat.

Strain through a fine mesh sieve into a medium bowl.

Stir in butter and vanilla. Cover surface with plastic wrap. Refrigerate 1 to 2 hours or until chilled**. (Lemon curd can be made up to a week ahead.) Reserve 1/4 cup lemon curd before assembling tiramisu.

For Syrup: Combine 1 1/2 cup sugar, lemon peel, lemon juice and limoncello in a small non-reative* saucepan. Bring to a boil over medium-high heat, stirring occasionally. Cook until sugar melts.

Discard the lemon peel. Transfer syrup to a glass bow or 4-cup glass measuring cup. Set syrup aside to cool.

For Mascarpone Layer: Beat cream and powdered sugar in a large bowl until stiff peaks form. Set aside.

Beat mascarpone and lemon zest in an extra-large bowl until combined and creamy. Fold in 3/4 cup lemon curd.

Fold the whipped cream into the mascarpone mixture in three batches, folding gently until everything is combined.

Arrange half of the  ladyfingers in a single layer on the bottom of a 9×13-inch baking dish, trimming ladyfingers as needed. Generously brush or drizzle half the syrup over the ladyfingers.

Top the ladyfingers with half of the remaining lemon curd.

Layer half of the mascarpone filling over lemon curd.

Repeat with remaining lady fingers, lemon curd, and mascarpone filling.

Drizzle reserved lemon curd over tiramisu. (You will use about 10 oz. ladyfingers. Save remaining ladyfingers for another purpose.)

Cover with plastic wrap and chill in the refrigerator at least 8 hours or overnight before serving. Slice and enjoy!