• 125g unsalted butter, chopped, at room temperature
• 1½ cups caster sugar
• 2 tsps finely grated lemon rind
• 6 eggs, separated
• ⅔ cup self-raising flour
• ⅔ cup lemon juice
• 1½ cups milk
Grease inside the ceramic removable bowl of a 5 to 6-litre slow cooker.
Beat butter, sugar and rind in the small bowl of an electric mixer until combined. Beat in yolks, one at a time, until combined. Add flour, lemon juice and milk. Beat on low speed until just combined. Transfer to a large bowl.
Beat egg whites in same, clean bowl of electric mixer until firm peaks form. Gently fold into lemon mixture, in two batches, until just combined. Pour the mixture into prepared bowl in the slow cooker. Cover with lid.
Cook on high for about 1½ hours to 1¾ hours, or until sponge topping is cooked and dark brown around the edge. Remove bowl from slow cooker. Stand pudding in bowl for 5 minutes before serving.
Dust pudding with sifted icing sugar and serve with ice cream, if desired.