Place the butter in a bowl and whisk vigorously until it gets creamy white.

Place the egg yolks in another bowl with the sugar and beat until they become fluffy, follow by adding the mixture to the butter and mix, then add the brandy.

Place the juice and the baking soda in a large bolw and mix, when it foams add the juice to the bowl with the butter.

Beat the egg whites in a clean bowl until they form stiff peaks and then add them to the butter. Mix well and then add the orange zest and the baking powder. Add the flour gradually until you have a soft thick batter.

Pour it into a round baking tray that you have brushed with butter and bake at 200°C for 50-60 minutes (make sure that it is ready by piercing it with a clean dry knife at the center. The knife has to come out clean).

Remove, let it cool lightly and take it out of the baking tray.

Sprinkle with icing sugar and serve.