Preheat the oven to 350°F (175°C). Grease a 9x5 inch loaf pan thoroughly and line the bottom and long sides with a parchment sling for easy removal.
In a medium bowl, whisk together the flour, baking powder, baking soda, and salt.
Toss the blueberries with the reserved tablespoon of flour until lightly coated. Set aside.
In a large bowl, beat the softened butter and sugar on medium-high speed for 3-4 minutes until pale and fluffy.
Beat in the eggs one at a time, then mix in the vanilla, lemon zest, and lemon juice.
Mix in the sour cream on low speed until just incorporated.
Fold the dry ingredients into the wet with a spatula until no large streaks of flour remain. Be careful not to overmix.
Fold the flour-coated blueberries gently into the batter with a few strokes.
Pour the batter into the prepared pan and smooth the top. Bake on the center rack for 55-65 minutes.
Check for doneness with a toothpick; it should come out clean or with a few moist crumbs. Tent with foil if the top browns too quickly.
Cool the loaf in the pan for 15 minutes, then lift it out using the parchment sling and cool completely on a rack.
Whisk together the sifted powdered sugar and lemon juice until smooth and pourable. Drizzle over the cooled loaf and let set for 10 minutes.