2 unwaxed lemons, finely grated zest only
juice of 2 lemons, strained
250g/9oz plain flour
½ tsp baking powder
½ tsp bicarbonate of soda
125²µ/4½´Ç³ú caster sugar
2 tbsp icing sugar
1 tbsp granulated sugar
100g/3½oz unsalted butter, melted
2 large free-range eggs
200g/7oz plain, full-fat yoghurt