Finely zest the lemon and squeeze its juice.

Beat mascarpone cheese, powdered sugar, lemon zest, and lemon juice until smooth.

Add the cold heavy cream and beat until a thick cream forms.

Pour the lemonade into a shallow bowl for dipping.

Spread a thin layer of mascarpone cream in the dessert bowl.

Briefly dip each Maria biscuit in lemonade and arrange it over the cream.

Alternate mascarpone cream and dipped biscuits until the dessert bowl is filled.

Sprinkle lime zest and crushed Maria biscuits over the final cream layer.

Chill the tiramisu until very cold, then serve.