Begin by preheating your oven to 400°F (200°C). Line a baking sheet with parchment paper to prevent sticking.
In a large mixing bowl, combine the all-purpose flour, granulated sugar, baking powder, and salt. Whisk the dry ingredients together until they are well blended and airy.
Add the cold, cubed butter into the flour mixture. Using a pastry cutter or your fingertips, incorporate the butter until the mixture resembles coarse crumbs, with bits of butter no larger than pea-sized.
Carefully fold in the fresh blueberries and the lemon zest using a spatula, ensuring that the fruit is evenly dispersed throughout the mixture without breaking them.
In a separate small bowl, whisk together the chilled buttermilk, egg, vanilla extract, and fresh lemon juice until the mixture is smooth and combined.
Pour the buttermilk mixture into the bowl with the flour mixture. Gently stir using a wooden spoon or spatula until the dough is just combined. Avoid over-mixing; the dough should remain slightly sticky and lumpy.
Transfer the dough onto a lightly floured surface. Pat the dough into a circle about 1-inch thick. Cut the dough into 8 wedges, or alternatively, use a round cutter to create individual scones.
Place the shaped scones onto the prepared baking sheet. Lightly brush the tops of the scones with a splash of buttermilk and generously sprinkle coarse sugar on top for a crunchy finish.
Bake in the preheated oven for 15-20 minutes, or until the scones are golden brown, and a toothpick inserted into the center comes out clean.
Once baked, remove the scones from the oven and transfer them to a wire rack to cool for a few minutes before serving.