½ unwaxed lemon, zest only
125²µ/4½´Ç³ú caster sugar
40²µ/1½´Ç³ú ground almonds
icing sugar, for dusting
pinch salt
1 tsp vanilla extract
200g/7oz gluten-free plain flour, plus extra for rolling
125²µ/4½´Ç³ú unsalted butter, at room temperature
1 free-range egg, lightly beaten