Rub sugar and orange zest together. Add the sugar and orange zest into a large mixing bowl, then use your fingertips to rub the zest into the sugar to release the oils.
Sift in dry ingredients. Line a baking tray with parchment paper. Into the large mixing bowl, sift in your dry ingredients; flour, baking powder and salt. Stir together.
Whisk wet ingredients together. In a bowl, whisk together the buttermilk, egg and vanilla extract. Once whisked, set aside one tablespoon of the egg mixture- this will be your egg wash to be used later.
Add butter to flour. Add the chopped butter to the mixing bowl and using your fingertips, toss the pieces until they are separated and coated with flour. Using your fingertips, rub the flour and butter together, leaving some larger butter bits.
Combine wet with the dry ingredients. Make a well in the dry mix and pour in the whisked egg and milk mixture into the centre. Use a fork to stir until the mixture starts forming a shaggy dough.
Coat the cranberries in flour. Add the remaining 1 tablespoon of flour into the bowl and toss to coat the cranberries. Add to the dough and gently mix in with your fingertips. Then start to press the dough together.
Bring the dough together. Tip the dough out onto a lightly floured work surface, and continue to press together with floured hands. Fold it in half and then press flat. Try not to knead the dough. Gently flatten it out into a disc.
Cut the dough in half and shape it into two discs. Using a bench scraper or a sharp knife, cut the dough in two. Shape each half into a round disc. Flatten the disc until it's 2 cm (1-inch) thick.
Prepare scone rounds and refrigerate. Add the two discs onto the prepared baking tray. Refrigerate the tray for 30 minutes or freeze them for 15 minutes. Whilst the scones are chilling, preheat the oven to 180°C (350°F)Brush each disc with the remaining egg mixture. Sprinkle the tops with demerara sugar. Cut each disc into 6 wedges using a sharp knife. Re-position wedges on the tray so that they sit one inch apart. Bake. Bake for 25-35 minutes until the scones are risen and the tops are golden brown. Once baked, remove from the oven.
Make glaze. Add powdered sugar and orange juice to a bowl and whisk until smooth. Drizzle glaze over scones. Serve immediately. Best eaten the day they are made.