Preheat your oven to 425°F (220°C) and line a baking sheet with parchment paper.
In a large mixing bowl, whisk together the flour, baking powder, salt, and granulated sugar until well combined.
Add the cold, cubed butter to the flour mixture. Using a pastry cutter or your fingertips, mix until the mixture resembles coarse crumbs with some pea-sized pieces of butter remaining.
In a separate bowl, combine the buttermilk, vanilla extract, and lemon zest (if using).
Pour the buttermilk mixture into the flour mixture and gently stir until just combined. Be careful not to overmix.
Fold in the fresh blueberries, ensuring they are evenly distributed throughout the dough.
Lightly flour a clean surface and turn the dough out onto it. Pat the dough into a rectangle about 1-inch thick.
Using a biscuit cutter or a floured glass, cut out the biscuits and place them on the prepared baking sheet. Gather and re-pat the scraps to cut out additional biscuits.
Bake in the preheated oven for 12-15 minutes or until the biscuits are golden brown on top.
Allow the biscuits to cool slightly before serving.
Notes
Serve warm with a drizzle of honey or a smear of butter, and garnish with extra blueberries on top for a pop of color.