Set oven rack to the centre of the oven. Preheat to 500°F. Use two baking sheets to prevent over browning. Line baking pan with parchment then transfer parchment directly onto the counter. Spray or brush with oil.
In a large bowl measure flour, sugar, baking powder, salt and xanthan gum. Whisk until combined.
Using a stand mixer, food processor or your hands, add cold butter and mix until the mixture resembles fine crumbs with no butter pieces visible.
Stir in cranberries and orange zest.
In a measuring cup stir sour cream and egg until combined. Stir into dry ingredients and mix until combined. Cover bowl and let rest for 30 minutes.
Transfer dough to greased parchment paper. Using wet hands shape the dough into a 6-inch round about 1-inch thick.**
Grease a large knife and cut into 6 or 8 wedges. Transfer parchment to baking sheet and arrange scones 2-inches apart. Lightly sprinkle tops with a little extra sugar.
Transfer to oven and immediately reduce temperature to 425°F. Bake until golden brown, 15-18 minutes.
Cool on a baking rack 5-10 minutes before eating. When completely cooked store in airtight container.