Begin by preheating your oven to 425°F (220°C) and prepare a baking sheet by lining it with parchment paper to prevent sticking.
In a large mixing bowl, whisk together the all-purpose flour, baking powder, salt, and granulated sugar until well incorporated, ensuring there are no lumps.
Add the cold, cubed butter to your flour mixture. Using a pastry cutter or your fingertips, combine the butter with the dry ingredients until the mixture resembles coarse crumbs, with some pea-sized pieces of butter remaining for a flaky texture.
In a separate bowl, whisk together the buttermilk, vanilla extract, and the optional lemon zest until smoothly blended.
Carefully pour the buttermilk mixture into the flour and butter combination. Gently stir the ingredients together with a spatula or wooden spoon until just combined. Avoid overmixing to keep your biscuits light and fluffy.
Gently fold in the fresh blueberries, ensuring they are evenly distributed throughout the dough without crushing them.
Lightly flour a clean work surface and turn the dough out onto it. Pat the dough down into a rectangle approximately 1 inch thick, being careful not to overwork it.
Using a biscuit cutter or a floured glass, cut out the biscuits and transfer them to the prepared baking sheet. Gather any scraps, re-pat them into a rectangle, and continue cutting out additional biscuits.
Place the baking sheet in the preheated oven and bake for 12 to 15 minutes, or until the tops of the biscuits turn a lovely golden brown.
Once baked, remove the biscuits from the oven and allow them to cool slightly on the baking sheet before serving.
Notes
Serve warm drizzled with honey or spread with butter. Garnish with extra blueberries for visual appeal.