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.
Combine the 1/2 c. sugar and 2 tsp. cinnamon and set aside.
Place a small amount of batter in tin, add desired amount of the cinnamon & sugar mixture (we like a lot ☺, probably a 1 tsp. or so), then add another small amount of the batter on top. Sprinkle lightly with the cinnamon mixture.
Bake at 350° for 15 minutes, or until done.