In a large bowl, whisk together the flour, baking powder, salt, and lemon zest.
Add the cold butter.
Rub it into the flour mixture with your fingertips, a fork or a pastry cutter, until it resembles coarse crumbs.
Add the egg, Greek yogurt, honey and vanilla extract (if using).
Gently mix until the dough just starts to come together. If it seems too dry, add another 1–2 tablespoons of milk, one tablespoon at a time.
Gently fold in the blueberries, being careful not to crush them.
Optional, chill the dough for 20-30 minutes before baking. This helps them bake up taller with a flakier texture.
Meanwhile, preheat the oven to 400°F (200°C). Line a baking tray with parchment paper.
Transfer the dough to a lightly floured surface and gently pat it into an 8-inch (20 cm) circle, about 1 inch (2.5 cm) thick. Avoid overworking the dough.
Cut the dough into 8 wedges and place them on the prepared baking tray, leaving a little space between each one.
Brush the tops with beaten egg.
Bake for 20–25 minutes, or until the tops are golden brown and the scones are cooked through.
Let the scones cool on the baking tray for 5 minutes, then transfer them to a wire rack. Serve warm or at room temperature.