1 3/4 cups (245 g) all purpose gluten free flour, plus more for sprinkling
1 teaspoon xanthan gum (omit if your blend already contains it)
1/4 cup (36 g) cornstarch
2 teaspoons baking powder
1/4 teaspoon baking soda
1/2 teaspoon kosher salt
2 teaspoons (12 g) granulated sugar, plus more for sprinkling
Freshly grated lemon zest from 1 medium lemon
5 tablespoons (70 g) unsalted butter, chopped into small chunks and chilled
1 cup (180 g) fresh blueberries
3/4 cup (6 fluid ounces) milk, plus more for brushing
1 tablespoon freshly squeezed lemon juice
2 tablespoons (42 g) honey
Preheat your oven to 400°F. Line a rimmed baking sheet with unbleached parchment paper and set it aside.
In a large bowl, place the flour, xanthan gum, cornstarch, baking powder, baking soda, salt, granulated sugar, and lemon zest, and whisk to combine well. Add the chopped and chilled butter, and toss to coat it in the dry ingredients. Flatten each chunk of butter between your thumb and forefinger. Add the blueberries, and toss to coat. Create a well in the center of the dry ingredients and add the milk, lemon juice, and honey. Mix gently until the dough begins to come together. If necessary, press together into a dough with floured hands, handling the dough as little as possible. Turn out the dough onto a large piece of plastic wrap and press into a disk that’s about 7 inches in diameter. Wrap the disk tightly in the plastic wrap and place in the freezer to chill for about 10 minutes or until firm.
Remove the dough from the freezer, unwrap it, sprinkle the top with about 1 teaspoonful additional flour and spread out over the top of the disk. Using a large, sharp knife or a bench scraper, cut the dough into 2 equal halves, then each of those halves into 3 equal triangles. Place the wedges about 2 inches apart from one another on the prepared baking sheet, and using a pastry brush, paint the tops generously with milk. Sprinkle the tops generously with granulated sugar.
Place the baking sheet in the center of the preheated oven and bake until the scones are puffed, very pale golden all over and slightly more brown on the edges and top (about 20 minutes). Remove from the oven and allow to cool for 10 minutes on the baking sheet before serving.