Preheat the oven to 425°F. Line a 12-cup muffin pan with cupcake liners or spray with non-stick cooking spray.
Sift together the flour, salt, and baking powder in a small bowl and set aside.
In a large mixing bowl, beat or whisk together the eggs, melted butter, sugar, vanilla extract, buttermilk, and sour cream.
Dump the dry ingredients into the butter and sour cream mixture and stir gently, just until combined. Do not overmix.
Toss 1 cup of blueberries with the remaining tablespoon of flour and fold into the muffin batter.
Divide the batter between the 12 muffin cups in the prepared pan, filling each cup about ¾ of the way full.
Sprinkle brown sugar over the top of the muffins.
Bake for 6 to 7 minutes at 425°F and then turn the oven down to 375°F and continue baking an additional 10 to 12 minutes until a toothpick inserted in the center of the muffins comes out clean and the tops are golden brown.
Cool muffins in pan for 5 minutes. Remove muffins to a cooling rack to finish cooling.
