"Light" Citrus Sponge Cake

Directions

1. 1
   First make the sponge. In a bowl, mix the flour, salt and baking powder and set aside. In a separate bowl, beat the 3 egg yolks until thick and add 3/4 cup sugar. Continue beating until the egg mixture is thick and pale. Add vanilla and orange juice, beating at low speed until blended.
2. 2
   Beat 5 egg whites until foaming and beginning to form soft peaks, then slowly incorporate remaining 1/4 cup sugar, 1 teaspoon at a time, beating well between each addition. When all the sugar has been added, the mixture should be thick and glossy.
3. 3
   Mix a little egg white into the cake batter and mix gently then incorporate the remaining whites into the cake batter. Mix gently and carefully to combine. Pour the mixture into a greased (and lined) Kugelhopf or Angel Food tin and bake at 180c. for 30-40 minutes. When cooked, the cake will spring back when lightly pressed. Allow to cool on a wire rack.
4. 4
   Make the filling: In a saucepan, mix sugar, custard powder and salt and whisk with the milk. Bring to the boil slowly, stirring often. When bubbles begin to form around the edge of the pan, stir constantly while the custard thickens, about 1 minute. Remove pan from the heat and stir in the lemon rind and juice.Cover and chill
5. 5
   Make the frosting: In a stainless steel bowl, combine all ingredients and whisk with a hand mixer. Place the bowl over simmering water in a saucepan and using a hand mixer, begin to mix on high speed. Continue heating and mixing for about 8 minutes until the frosting mixture is thick and stiff peaks form.
6. 6
   Remove from heat and add vanilla, mix to combine.
7. 7
   Beat for 1 further minute until the frosting is a spreadable consistency.
8. 8
   To assemble, cut cold cake horizontally into three layers. Spread half the lemon filling on the base then top with the middle layer. Spread the remaining lemon filling on the middle layer then top with the final layer. Spread frosting over sides and top of cake, enclosing cake totally.
9. 9
   Decorate with lemon slices and rind or for a more elegant finish, simmer the lemon slices in 2 tablespoons water and 4 tablespoons sugar for 4 minutes until shiny and opaque. Drain well, allow to cool and place on frosting.