Preheat your oven to 375°F.
Line a baking sheet with parchment paper.
In a large bowl, whisk together the flour, sugar, baking powder, salt, and lemon zest.
Cut in the cold butter using a pastry blender or your fingers until the mixture resembles coarse crumbs.
In a small bowl or measuring cup, whisk together the egg, milk, and vanilla. Add to the dry ingredients and mix just until combined.
Gently fold in the blueberries, being careful not to overmix.
On a lightly floured surface, shape the dough into a circle about 1 inch thick. Cut into 8 wedges and place on the baking sheet.
Brush the tops with a bit of milk. Optional: sprinkle a little sugar for crunch.
Bake for 18–22 minutes or until golden brown. Cool slightly and enjoy!