Preheat oven to 400°F (200°C) and line a baking sheet with parchment. Whisk flour, sugar, baking powder, and salt in a large bowl.

Cut cold butter into the dry mix with a pastry cutter or your fingers until coarse crumbs form with a few pea-sized bits.

Whisk buttermilk, egg, vanilla, and zest together. Pour into the flour mixture, add frozen blueberries, and fold gently just until combined.

Pat dough into a ¾-inch-thick disk on the baking sheet, cut into 8 wedges, and separate them slightly.

Brush tops with buttermilk and bake 16 to 19 minutes until golden. Cool on the pan 5 minutes.

Whisk powdered sugar with lemon juice to a thick honey consistency. Drizzle over warm scones and serve.