Preheat your oven to 350°F (175°C) and line a muffin tin with cupcake liners.
In a mixing bowl, whisk together the flour, baking powder, baking soda, and salt.
In another bowl, beat the butter and sugar until light and fluffy. Add the eggs one at a time, beating well after each addition.
Mix in the mashed bananas, sour cream, and vanilla extract until well combined.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Divide the batter evenly among the cupcake liners, filling each about two-thirds full.
Bake for 18-20 minutes, or until a toothpick inserted into the center comes out clean.
Allow the cupcakes to cool in the tin for 5 minutes, then transfer to a wire rack to cool completely.