In a bowl, whisk together the eggs, white sugar, lemon juice, and lemon zest until well combined.

Pour the mixture into a small saucepan. Cook over low heat, stirring constantly with a spatula or whisk, until the mixture thickens enough. Remove from heat, add the butter, and stir until completely melted and smooth.

Strain the curd through a fine-mesh sieve into a clean bowl to remove any zest or cooked egg bits. Let cool completely to room temperature.

In a small saucepan, combine the water, sugar, lemon juice, and lemon zest. Bring to a boil over medium heat, stirring occasionally until the sugar dissolves. Remove from heat and let cool to room temperature.

Place the egg yolks and white sugar in a heatproof bowl. Set the bowl over a pot of simmering water (double boiler method). Whisk continuously until the mixture becomes thick, pale, and creamy—this also pasteurizes the eggs. If you are using pasteurized or sterilized eggs, you may skip this step. Remove from heat.

In a separate large bowl, beat the mascarpone cheese with a spatula or hand mixer until smooth and creamy. Add the egg yolk mixture in two batches, mixing well after each addition until fully combined. Add 55g of the cooled lemon curd and stir until evenly incorporated.

In a chilled bowl, whip the heavy cream with a hand mixer or stand mixer fitted with a whisk attachment until it reaches a yogurt-like consistency—soft, thick, and billowy but not stiff.

Gently fold the whipped cream into the mascarpone-lemon mixture using a spatula. Use a folding motion (cutting down through the center and lifting up from the bottom) until no streaks remain and the mixture is uniform in color and texture.

Pour the cooled lemon syrup into a shallow dish. Quickly dip each ladyfinger into the syrup—just a brief dip on both sides—and arrange a single layer in the bottom of your mold.

Brush a thin layer of lemon curd over the ladyfingers.

Pipe or spoon half of the cheese and cream mixture over the top and spread it evenly with a spatula.

Repeat with another layer of syrup-dipped ladyfingers, another brush of lemon curd, and the remaining cheese mixture.

Smooth the top, then use the back of a spoon to create decorative (indented) swirls or wavy patterns across the surface.

Cover the mold with a lid or plastic wrap and refrigerate overnight (at least 8 hours). This allows the tiramisu to firm up and the flavors to meld beautifully.

Just before serving, garnish the top with fresh lemon zest and a few small lemon wedges or lemon slices for a bright, beautiful finish.