Step 1: Prep Your Pan and Oven
Preheat your oven to 350°F (175°C). Line a 9×5-inch loaf pan with parchment paper, leaving overhang on the long sides for easy removal, or thoroughly grease and flour the pan. Set aside.

Step 2: Mix Dry Ingredients
In a medium bowl, whisk together 1¾ cups flour, baking powder, baking soda, and salt until well combined. Set aside.

Step 3: Prepare Lemon Sugar
In a large mixing bowl, combine the granulated sugar and lemon zest. Use your fingers to rub the zest into the sugar for about 30 seconds—this releases the aromatic lemon oils and infuses the sugar with intense lemon flavor. This step makes a huge difference!

Step 4: Mix Wet Ingredients
To the lemon sugar, add the melted butter and whisk until combined. Add eggs one at a time, whisking well after each addition. Add sour cream, lemon juice, milk, and vanilla extract. Whisk until the mixture is smooth and well combined. It may look slightly curdled from the lemon juice—this is completely normal and fine!

Step 5: Combine Wet and Dry
Pour the dry ingredients into the wet ingredients. Using a rubber spatula or wooden spoon, gently fold everything together until just combined and no dry flour streaks remain. Do not overmix! The batter should be thick and slightly lumpy. Overmixing develops gluten, which creates tough, dense quick bread.

Step 6: Fold in Blueberries
In a small bowl, toss the blueberries with the remaining 1 tablespoon of flour until coated—this prevents them from sinking to the bottom. Gently fold the floured blueberries into the batter using a spatula, being careful not to crush them. Fold just until evenly distributed.

Step 7: Bake
Pour the batter into your prepared loaf pan, spreading it evenly. Tap the pan gently on the counter a few times to release any air bubbles. Bake for 55-65 minutes, or until the top is golden brown, the loaf has risen nicely with a crack down the center, and a toothpick inserted into the center comes out clean or with just a few moist crumbs (no wet batter). If the top is browning too quickly, loosely tent with aluminum foil after 40 minutes.

Step 8: Cool the Loaf
Remove from the oven and let the loaf cool in the pan on a wire rack for 15-20 minutes. Then, using the parchment paper overhang, carefully lift the loaf out of the pan and transfer to the wire rack to cool completely before glazing. This takes about 1-2 hours. Don’t skip cooling completely—glazing a warm loaf will cause the glaze to soak in and become invisible.

Step 9: Make the Lemon Glaze
Once the loaf is completely cool, make the glaze. In a small bowl, whisk together the powdered sugar and 2 tablespoons of lemon juice until smooth. The glaze should be thick but pourable—if too thick, add more lemon juice a teaspoon at a time; if too thin, add more powdered sugar. Stir in the optional lemon zest for extra flavor and visual appeal.

Step 10: Glaze and Serve
Drizzle or spread the glaze over the top of the cooled loaf, letting it drip down the sides naturally for a beautiful presentation. Let the glaze set for about 10-15 minutes before slicing. Cut into thick slices and serve!