- Whisk egg whites and tartar cream together until stiff.
- Sift flour, with baking powder and salt.
- Add sugar, then oil, egg yolks, water, lemon juice and orange rind, one by one.
- Beat the two mixtures together with an electric beater until smooth.
- Pour into a pan and bake at 160C for an hour and 10 minutes.
- Remove from oven and let it cool.