Preheat oven to 400°F (200°C) and line a baking sheet with parchment paper.
In a large bowl, whisk flour, sugar, salt, and baking powder.
Stir in lemon zest.
Cut in cold butter until mixture resembles coarse crumbs.
In a separate bowl, whisk heavy cream, egg, and vanilla extract.
Add wet ingredients to dry ingredients and mix gently until combined.
Fold in blueberries carefully.
Shape dough into a 1-inch thick circle and cut into 8 wedges.
Place on baking sheet and brush tops with reserved heavy cream.
Bake 18–22 minutes until golden.
Whisk glaze ingredients together and drizzle over cooled scones.