Preheat oven to 400°F and line a baking sheet with parchment paper.
In a large bowl, whisk together the flours, baking powder, salt, and sugar.
Add cold butter cubes and use a pastry cutter or your fingers to mix until the texture resembles coarse crumbs.
In a separate bowl, whisk together the Greek yogurt, milk, egg, vanilla, and lemon zest (if using).
Pour wet ingredients into dry ingredients and gently mix until just combined.. Carefully fold in the blueberries. If using frozen, do not thaw before using.
Transfer dough to a floured surface and gently form into a round disc about 1 inch thick. Place on prepared baking sheet and cut into 8 wedges, leaving them together in the circle for baking.
Bake for 18–22 minutes, or until golden brown on top and firm to the touch. Let cool slightly.
In a small bowl, whisk together the powdered sugar, milk or lemon juice, vanilla extract, and salt. Drizzle over slightly cooled scones.