Heat oven to 220C/200C fan/gas 7. Put the flour, salt and butter in a food processor and pulse until you can’t feel any lumps of butter (or rub in any remaining lumps with your fingers).
Finely chop 50g pistachios and add them to the pulsed dry flour mixture with 3 tbsp golden caster sugar.
Stir the buttermilk into the mixture and use a knife to quickly combine everything together to form a dough – stop when it has just combined and don’t overmix it.
Tip the dough onto a floured surface and lightly bring it together with your hands a couple of times. Press out gently until about 4cm thick, then stamp out 6-7cm rounds. Re-shape any trimmings until all the dough is used. Spread out on a lightly floured baking sheet and bake for 10-12 mins or until well risen and golden.
When the scones are cooked, mix enough icing sugar into the juice of ½ a lemon to make a thick glaze, then drizzle it liberally over the scones.