Preheat your oven to 425°F (218°C). Line a baking sheet with parchment paper. Set aside.
In a large mixing bowl, whisk together 2 cups (280 g) gluten-free flour blend, ½ cup (100 g) granulated sugar, 1 tablespoon baking powder, ½ teaspoon ground cinnamon and ½ teaspoon salt until combined.
Add 6 tablespoons (84 g) unsalted butter (cold and cubed) to the flour mixture. Using a pastry cutter or two knives, cut the butter into the flour until the mixture is crumbly and the butter pieces are about the size of peas. Some larger pieces are fine. Work quickly so the butter stays cold.
Add 6 oz (170 g) fresh blackberries to the flour mixture and toss until they are coated with the flour. This helps prevent the berries from bleeding too much into the dough.
In a separate small bowl, whisk together ⅓ of the ½ cup (120 g) whole milk, 1 (50 g) large egg, and 1 teaspoon vanilla extract until smooth.
Pour the milk mixture into the flour mixture and stir with a fork or wooden spoon to combine. The dough should be scraggly, not smooth. If there's still loose flour on the bottom of the bowl and the dough won't come together, add more milk 1 tablespoon at a time, drizzling it over the dry spots. Stop when you can form a mass with no more loose flour in the bowl. Don't overwork the dough or the blackberries will bleed and the scones will turn out dense.
Turn the dough out onto a lightly floured surface. Shape it into a circle about 1.5 inches thick and 6 inches wide. The dough should be thick because scones don't rise much.
Use a sharp knife to cut the circle into 8 equal wedges, like cutting a pizza.
Transfer the wedges to the prepared baking sheet, leaving about 2 inches of space between them so they have room to expand slightly.
Brush the tops of the scones with 1 tablespoon (14 g) melted butter. Sprinkle with 2 teaspoons (8 g) turbinado sugar.
Bake the scones in the preheated oven at 425℉ for 18-20 minutes, until the scones are golden brown and a toothpick inserted into the center comes out clean.
Remove from the oven and let cool on the baking sheet for at least 10 minutes before serving.