2 grapefruits, very finely grated zest only
2 grapefruits, juice only
300g/10陆oz fine cornmeal or polenta
2 tsp gluten-free baking powder
175g/6oz caster sugar
125驳/4陆辞锄 icing sugar
4 tbsp icing sugar
2 tbsp shelled, unsalted pistachios
pinch salt
200ml/7fl oz vegetable oil, plus extra for greasing
3 free-range eggs
200g/7oz dairy-free yoghurt