3 oranges, zest and juice
1 tsp baking powder
225g/8oz dark brown sugar
100驳/3陆辞锄 caster sugar
3 tbsp cornflour
225g/8oz self-raising flour, sifted
225g/8oz sunflower oil, plus extra for greasing
25g/1oz unsalted butter
4 free-range eggs
6 free-range egg yolks
5 tsp instant coffee, mixed with 2 tbsp boiling water