Place the rice flour, cornflour, baking powder, bicarbonate of soda and butter in a food processor and whizz until the mixture resembles fine breadcrumbs. Alternatively, mix together the dry ingredients in a large bowl. Add the butter and rub in with the fingertips until the mixture resembles fine breadcrumbs. Mix in the spinach, sun-dried tomatoes, Parmesan and nutmeg.
Whisk together the egg and buttermilk with a fork in a separate bowl, stir in the flour mixture and combine to form a soft dough.
Turn the dough out on a surface lightly dusted with rice flour, press out to a thickness of 2.5 cm (1 inch) and use a 5 cm (2 inch) cutter to stamp out 8 scones, rerolling the trimmings as necessary.
Put on a baking sheet lightly dusted with rice flour, brush with a little buttermilk and place in a preheated oven, 220°C (425°F), Gas Mark 7, for 12–15 minutes until risen and golden. Serve warm, spread with butter or to accompany the soup.