Prep the pan and oven: Heat the oven to 350°F (175°C). Line a 9x5-inch loaf pan with parchment paper, leaving a slight overhang for easy lifting. Lightly grease the sides.
Mix dry ingredients: In a medium bowl, whisk the flour (1 1/2 cups), baking powder, and salt.
Set aside.
Rub zest into sugar: In a large bowl, add the sugar and lemon zest. Use your fingers to rub the zest into the sugar until fragrant and slightly damp. This releases the oils and boosts flavor.
Combine wet ingredients: Whisk in the eggs, sour cream, oil, lemon juice, and vanilla until smooth and well blended.
Bring the batter together: Add the dry ingredients to the wet.
Stir gently with a spatula until just combined and no dry streaks remain. Do not overmix.
Prep the blueberries: Toss the blueberries with 1 tablespoon flour. Fold them into the batter using a few light strokes.
Reserve a few berries for the top if you like a dotted, bakery-style look.
Fill and bake: Spread the batter evenly in the pan. Scatter reserved berries on top. Bake for 50–60 minutes, or until the top is golden and a toothpick inserted into the center comes out clean or with a few moist crumbs.
Cool properly: Let the loaf cool in the pan for 10–15 minutes, then lift it out using the parchment and transfer to a wire rack to cool completely.
Glaze (optional): Whisk powdered sugar with lemon juice until smooth and pourable.
Stir in zest if using. Drizzle over the cooled loaf. Let set for 15 minutes before slicing.