Requires: 24cm round cake pan, electric mixer (or hand beater)
Preheat oven to 180°C conventional oven (350° Fahrenheit/Gas 4). Grease a 24cm round cake pan by lightly buttering the base and sides with margarine or butter. Line the base with baking paper, then lightly butter over the baking paper. Add a heaped tablespoon of 00 flour, then turn and shake the tin to coat the butter in flour on the base and sides of the cake pan.
Using an electric mixer or hand beater, beat the egg whites with a pinch of salt until stiff peaks form. With the mixer (or hand beater) running, add the egg yolks, one at a time. Add the sugar, one tablespoon at a time, beating well after each addition.
Use a wooden spoon to stir in the flour, one tablespoon at a time. You want to see air bubbles rise to the surface of the cake mixture before adding additional tablespoons of flour. Stir in the orange zest and orange juice. Then stir in the margarine (or butter) until well combined. Stir the sifted baking powder into the cake mixture.
Note: 00 is a powder-fine Italian type of flour. It is made from soft wheat varieties and is frequently used in Italian desserts and pastas. 00 flour is available in most supermarkets, Italian food stores and gourmet delicatessens.
Pour the cake mixture into the prepared cake pan. Bake for 25-30 mins or until a skewer inserted in centre comes out clean.
Once completely cooled, slice the whole cake in half horizontally. Place the bottom cake layer onto a serving plate. Set aside the top half. Use a spatula to spread the whole jar of sweet orange marmalade over the bottom half of the cake. Place the remaining cake on top of the marmalade layer.
Before serving, place the slice of orange in the middle of the cake and dust sifted icing sugar (confectioners’ sugar) on top. Twist the orange slice into an ‘S’ shape for decoration – buon appetito!