unsalted butter, chilled, diced, plus extra to serve
Preheat the oven to 200°C (400F). Dust a large baking tray with flour.
Sift the flour, baking soda, cinnamon and 1/2 teaspoon of salt into a large bowl and mix well. Add the butter and use your fingertips to rub it into the flour until the mixture resembles fine crumbs. Stir in the sugar, blueberries and buttermilk, and mix to form a dough.
Form the dough into a 20cm round. Mark 8 wedges in the dough with a knife. Bake for 20-25 minutes or until light golden. Allow to cool, cut the scones into 8, then split in half and spread with butter.