Preheat the oven to 375°F (190°C).
Line a 9×13 inch (23x33cm) metal mold with parchment paper, making sure to cover all four sides.

Melt the butter in a large saucepan over medium heat and add the flour.
Remove the saucepan from the heat and whisk in the milk, sugar, and grated lemon zest. Return to the heat and bring to a boil, then reduce the heat and simmer for about 2 minutes, stirring constantly.
Add a pinch of salt and whisk in the lemon juice.
Let cool for 10 minutes.
Add the egg yolks one at a time, whisking well after each addition. Set aside.

Place the egg whites in a large bowl and beat them with an electric mixer until they become frothy.
Continue beating, adding the sugar gradually, until the egg whites are shiny and form soft peaks.
Add a large spoonful of the lemon cream to the egg whites to loosen them, then fold in the remaining egg whites and the second quantity of flour.

Pour the mixture into the prepared mold and smooth the top.
Bake for 18-20 minutes, or until the soufflé is puffed and golden brown.
Remove from the mold and place on a clean tea towel dusted with powdered sugar (to prevent the soufflé from sticking). Remove the parchment paper and let cool.

Topping: Mix the 35% cream, mascarpone, and sugar, and whip until the topping is firm and smooth.
Add the limoncello and whip again.

Spread the soufflé with the topping and roll it up, starting from the short side, using the tea towel as a guide.
Let rest for 30 minutes, seam-side down, and refrigerate until serving time.
Cut the roll into slices and serve with fresh fruit, if desired.