Grease and flour muffin tins.
Mix flour, baking powder, baking soda, and salt; set aside.
Pour the 1 c. sugar into a large bowl, then add the melted butter.
Add eggs, vanilla, and sour cream, and mix well.
Stir in the flour mixture.
Gently fold in the blueberries. (Make sure if you're using frozen berries that you've rinsed them well and patted them dry first.)
Fill muffin cups 2/3 full, then sprinkle a teaspoon of sugar on top of each one.
Bake at 350° for 15 minutes, or until done.