Lemon tiramisu is made with lemon curd, lemon syrup, and mascarpone cheese. Leftovers keep in the refrigerator for 3 days.
1 1/2 cups lemon juice
2 cups white sugar
4 eggs
4 egg yolks
1/8 teaspoon salt
1 cup unsalted butter, cut into cubes
1/2 teaspoon vanilla extract
Syrup
1 1/2 cups white sugar
3 (1-inch) strips of lemon peel
1/2 cup lemon juice
2/3 cup limoncello liqueur
Mascarpone Layer
2 cups heavy cream
1/2 cup powdered sugar
24 ounces mascarpone cheese
1 tablespoon lemon zest
10 ounces crisp ladyfingers (about 39 larger or 57 smaller ladyfingers)
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.