- Preheat oven to 180°C. Line a 20cm round cake tin with cooking paper.
- Beat the egg whites and sugar in a large bowl until white and thick (before soft peak stage).
- Add the orange and lemon zest, then stir in the olive oil.
- Stir in the sifted flour alternately with the water and orange juice.
- Pour into the prepared tin.
- Bake for 45 minutes or until a skewer comes out clean.
- Leave in the tin for five minutes before turning out onto a cake rack to cool. Dust with icing sugar.