Step 1

To make the limoncello pastry cream, bring 250ml (1 cup) milk, 250ml (1 cup) cream and lemon rind just to the boil in a saucepan over medium heat. Remove from heat. Whisk sugar, cornflour, egg yolks and remaining milk in a heatproof bowl until well combined. Slowly pour hot milk mixture into yolk mixture, whisking constantly, until smooth. Pour into the pan and whisk over medium heat for 3-5 minutes or until thickened. Remove from heat. Whisk in butter and limoncello. Transfer to a bowl. Cover surface with plastic wrap. Place in the fridge for 3 hours or overnight to chill.

Step 2

Preheat oven to 180C/160C fan forced. Grease two 20cm (base size) round cake pans and line bases and sides with baking paper. Sift plain flour and cornflour together 3 times to aerate.

Step 3

Use an electric mixer fitted with a whisk attachment to beat eggs and salt on low speed until just combined. Add sugar and lemon rind. Beat on low speed until combined, then increase speed to high. Beat for 15 minutes, or until mixture is thick, pale and tripled in volume. Add food colouring, if using, and beat until well combined.

Step 4

Gradually sift the flour mixture over the egg mixture and gently fold in with a large metal spoon or silicone spatula until just combined. Divide mixture between prepared pans. To level batter, gently spin tins on the kitchen bench. Bake for 30 minutes or until cake tops spring back when lightly touched. Set aside in pans for 10 minutes to cool slightly. Line a wire rack with baking paper. Turn sponges, top-side up, onto the rack to cool completely.

Step 5

To make the limoncello sugar syrup, stir water and caster sugar in a small saucepan over medium heat until the sugar dissolves. Bring to the boil and cook for 1 minute. Remove from heat and stir in the limoncello. Set aside to cool completely.

Step 6

Use a serrated bread knife to cut 1 cake horizontally into 3 even layers and set aside. Trim the top and side from the remaining cake to remove the brown crust. Cut the cake vertically into 1.5cm thick slices. Lay 1 cake slice flat and cut lengthways into 3 long strips. Cut strips into 1.5cm cubes. Repeat with remaining cake slices. Place cake cubes in a bowl and set aside.

Step 7

Use electric beaters to beat custard until smooth. In a separate bowl, whip remaining 250ml (1 cup) cream and extra caster sugar to just firm peaks. Use a spatula to fold cream mixture into custard until combined.

Step 8

Place 1 cake layer, cut-side up, on a serving plate or cake board. Use a pastry brush to brush cake with one-third of the limoncello sugar syrup. Use an offset palate knife or spatula to spread cake with one-third of the limoncello pastry cream. Repeat layering with another cake layer, limoncello sugar syrup and limoncello pastry cream, then finish with the cake top, cut-side down. Cover top and side of cake with remaining pastry cream and smooth with an offset palate knife or spatula. Press cake cubes over top and side of cake. Place cake in the fridge, covered, for 2-3 hours or overnight to set. Dust with icing sugar and decorate with lemon rind just before serving, if desired.