Preheat an oven to 425 F. Combine the dry ingredients from the all-purpose flour to the kosher salt in a large mixing bowl.
Whisk the wet ingredients from the melted butter to the eggs, including the sugar. Whisk in the sour cream, milk, and vanilla extract. Add the mixture to the dry ingredients and gently fold in until there are no visible flour clumps.
Toss the blueberries with powdered sugar. Gently fold in the fresh blueberries. Then divide the batter evenly between 8 muffin cups.
Sprinkle the muffin tops generously with the turbinado sugar. Bake the muffins for 7 minutes at 425 F. Then lower the heat to 350 F and bake for an additional 25-27 minutes.
Tips
Tossing the blueberries with powdered sugar will ensure the berries have a sweet, tangy flavor and not be overly sour.