Mix dry ingredients {flour through sugar} together in mixing ball.
Using a fork or pastry blender, 'cut in' the cubed butter into the flour mixture until coarse crumbs, roughly the size of peas, appear.
Add blueberries to mixture and stir gently.
In a small mixing bowl, whisk together the egg, vanilla, & buttermilk.
Make a well in the bottom of your flour mixture and pour in the liquid ingredients.
Gently stir with a wooden spoon until just barely mixed. If a few dry flour spots remain, that is great.
Line a baking sheet with parchment paper or Silpat liner and sprinkle lightly with GF flour mix.
Dump your scone dough onto the floured parchment paper.
Gently press your dough into a circular shape, roughly 1" in height.
Using a knife, cut the dough into 8 triangular pieces. Separate the pieces until a few inches apart and sprinkle sugar on top of each piece.
Place in the fridge for 30 minutes.
Bake in a preheated 400 degree oven for 18-20 minutes, rotating half way through.