Preheat the Oven:
Preheat your oven to 350°F (175°C). Grease and flour a 9×5-inch loaf pan or line it with parchment paper for easy removal.

Prepare the Dry Ingredients:
In a medium bowl, whisk together the all-purpose flour, baking powder, baking soda, and salt. Set aside.

Prepare the Blueberries:
In a small bowl, toss the fresh blueberries with 1 tablespoon of flour. This helps to prevent the blueberries from sinking to the bottom of the bread while baking. Set aside.

Cream the Butter and Sugar:
In a large bowl, beat together the softened butter and granulated sugar until light and fluffy, about 3-4 minutes. This step is important for the texture of the bread.

Add the Eggs and Vanilla:
Add the eggs, one at a time, beating well after each addition. Stir in the vanilla extract.

Combine Wet and Dry Ingredients:
With the mixer on low speed, alternately add the dry ingredients and the sour cream (or Greek yogurt) to the butter mixture, beginning and ending with the dry ingredients. Add the milk and mix until just combined. Be careful not to overmix.

Fold in the Blueberries:
Gently fold the floured blueberries into the batter with a spatula. Be careful not to overwork the batter, as this can cause the blueberries to break and the bread to become dense.

Bake the Bread:
Pour the batter into the prepared loaf pan and spread it evenly. Bake for 55-60 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs. If the bread starts to brown too quickly, tent it with aluminum foil and continue baking until done.

Cool the Bread:
Let the bread cool in the pan for 10 minutes before transferring it to a wire rack to cool completely.

Make the Lemon Glaze:
In a small bowl, whisk together the powdered sugar, fresh lemon juice, and lemon zest (if using) until smooth and well combined. If the glaze is too thick, add more lemon juice, 1 teaspoon at a time, until you reach your desired consistency.

Glaze the Bread:
Once the bread has cooled completely, drizzle the lemon glaze over the top. Allow the glaze to set for a few minutes before slicing and serving.