Follow these detailed steps carefully to ensure a perfectly moist and delicious blueberry lemon loaf every time. The key is to avoid overmixing the batter once the wet and dry ingredients are combined.

1. Preheat and Prepare: Begin by preheating your oven to 350°F (175°C). Grease a 9×5 inch loaf pan thoroughly with butter or non-stick cooking spray. For easy removal, you can also line the pan with parchment paper, leaving an overhang on the two long sides to act as “handles.”
2. Combine Dry Ingredients: In a large mixing bowl, add the 2 cups of all-purpose flour, 1 cup of granulated sugar, 1 ½ teaspoons of baking powder, and ½ teaspoon of salt. Use a whisk to stir these ingredients together for about 30 seconds. This process not only combines them evenly but also aerates the flour, much like sifting.
3. Prepare the Blueberries: In a separate small bowl, take your 1 ½ cups of fresh blueberries. Add 1 tablespoon of the dry flour mixture from the large bowl and gently toss the blueberries until they are lightly coated. This simple trick helps to suspend the berries within the batter, preventing them all from sinking to the bottom of the loaf during baking.
4. Combine Wet Ingredients: In a medium-sized bowl, whisk together the wet ingredients. Start with the single large egg, whisking it until it’s lightly beaten. Then, pour in the ½ cup of cooled melted butter, ½ cup of milk, 2 tablespoons of fresh lemon zest, 2 tablespoons of fresh lemon juice, and 1 teaspoon of vanilla extract. Whisk until everything is well combined and smooth.
5. Combine Wet and Dry: Pour the wet ingredient mixture into the large bowl containing the dry ingredients. Using a rubber spatula, gently fold the ingredients together. It is crucial that you mix only until the flour streaks have just disappeared. The batter will be thick and may look slightly lumpy—this is perfectly fine. Overmixing will develop the gluten in the flour, resulting in a tough, dense bread instead of a tender one.
6. Fold in the Blueberries: Gently fold the flour-coated blueberries into the batter. Use as few strokes as possible to distribute them evenly without crushing them or overmixing the batter.
7. Bake the Bread: Pour the finished batter into your prepared loaf pan and use the spatula to spread it evenly. Place the pan on the center rack of your preheated oven. Bake for 55 to 65 minutes.
8. Check for Doneness: At around the 55-minute mark, check the bread for doneness. Insert a wooden skewer or a long toothpick into the center of the loaf. If it comes out clean or with a few moist crumbs attached, the bread is done. If it comes out with wet batter, continue baking for another 5-10 minutes and check again. The top of the bread should be a deep golden brown and feel firm to the touch. If the top is browning too quickly before the inside is cooked, you can loosely tent it with a piece of aluminum foil for the remaining baking time.
9. Cool the Bread: Once baked, remove the loaf pan from the oven and place it on a wire cooling rack. Let the bread cool in the pan for at least 15-20 minutes. This allows the bread to set, making it easier to remove from the pan without breaking.
10. Prepare the Glaze: While the bread is cooling, prepare the lemon glaze. In a small bowl, whisk together 1 cup of powdered sugar and 2 tablespoons of fresh lemon juice. Start with 2 tablespoons and whisk until smooth. If the glaze is too thick, add more lemon juice, a ½ teaspoon at a time, until you reach your desired drizzling consistency. For extra flavor and visual appeal, stir in the optional ½ teaspoon of lemon zest.
11. Glaze and Serve: After the bread has cooled in the pan for 15-20 minutes, use the parchment paper handles (if used) or carefully invert the pan to remove the loaf. Place it directly on the wire cooling rack. While the bread is still warm, drizzle the lemon glaze all over the top, letting it drip down the sides. Allow the bread to cool completely before slicing and serving. This allows the crumb to fully set and the glaze to harden.