Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper.

In a large mixing bowl, whisk together the all-purpose flour, granulated sugar, baking powder, baking soda, and salt.

Add the cold, cubed butter to the dry ingredients. Use a pastry blender, two knives, or your fingertips to cut the butter into the flour mixture until it resembles coarse crumbs with some pea-sized pieces of butter remaining. This step is crucial for flaky scones.

In a separate small bowl, whisk together the sourdough discard, cold heavy cream, and vanilla extract.

Pour the wet ingredients into the dry ingredients. Mix with a spatula until just combined. Do not overmix; the dough will be shaggy.

Gently fold in the fresh blueberries and lemon zest until evenly distributed. Be careful not to crush the blueberries too much.

Turn the dough out onto a lightly floured surface. Gently pat the dough into an 8-inch round, about 1-inch thick. If the dough is too sticky, lightly flour your hands and the surface.

Using a sharp knife or a bench scraper, cut the round into 8 wedges (like a pizza).

Carefully transfer the scone wedges to the prepared baking sheet, spacing them about 1 inch apart. For an extra golden crust, brush the tops with a little extra heavy cream.

Bake for 18-22 minutes, or until the tops are golden brown and a scone inserted with a toothpick comes out clean (a few moist crumbs are okay). The exact time may vary depending on your oven.

Remove from the oven and let cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.

While the scones cool, if making the glaze, whisk together the powdered sugar and 2 tablespoons of milk or lemon juice in a small bowl until smooth. Add more liquid a teaspoon at a time if needed to reach your desired drizzling consistency.

Once the scones are completely cool, drizzle the glaze over them. Let the glaze set before serving.