Bring all the ingredients to room temperature.
Preheat the oven to 350°F.
Line a muffin tin with muffin paper.
Combine the dried ingredients in a bowl: flour, baking powder, baking soda, cinnamon and salt. Set aside.
Place the butter in a bowl and add both kinds of sugar. Mix for about 3 minutes on medium speed.
Stir in the vanilla and sour cream.
Add the eggs, one at a time.
Mash the bananas with a fork and add to the butter mixture.
Add the flour gradually and only mix until well combined.
Fill the muffin paper 2/3.
Bake for 20 minutes in the preheated oven.
Remove from the tray and place on a rack to cool completely.