Preheat your oven to 350°F (175°C) and generously grease a standard 9x5-inch loaf pan with butter or non-stick cooking spray.
In a medium bowl, whisk together the all-purpose flour, baking powder, baking soda, and kosher salt until well combined and set aside.
In a large mixing bowl, use an electric mixer on medium speed to cream together the softened butter and granulated sugar until the mixture is light, pale yellow, and fluffy, about 2-3 minutes.
Beat the room-temperature eggs into the butter mixture one at a time, followed by the sour cream and vanilla extract, mixing just until the wet ingredients are fully incorporated and smooth.
Gently fold the dry flour mixture into the wet ingredients with a spatula until almost combined, then add the blueberries and fold just until no dry streaks of flour remain, being careful not to overmix.
Scrape the batter into the prepared loaf pan and spread it into an even layer, then bake for 55-65 minutes, or until a toothpick inserted into the center of the loaf comes out clean.
Let the loaf cool in the pan on a wire rack for 20 minutes before carefully turning it out onto the rack to cool completely, which prevents it from becoming soggy.
Notes
Be careful not to overmix the batter to ensure a tender texture. Letting the loaf cool completely prevents it from becoming soggy.