Preheat oven to 350°F. Line a 12 cup muffin pan with paper liners.
In a medium bowl, whisk together the cake flour, baking powder, baking soda, salt and cinnamon.
In the bowl of a stand mixer fitted with the paddle attachment, or in a large bowl with an electric mixer, beat the butter and sugars on medium speed until light and fluffy - about 4 minutes.
Add in sour cream, vanilla and eggs and mix until combined.
Gradually add the flour mixture to the butter mixture and mix until just combined.
Fold in the mashed bananas until incorporated, taking care to not over mix.
Use a large cookie scoop (about 3 tablespoons) to divide the batter between the prepared muffin cups.
Bake cupcakes in preheated oven for 18-20 minutes, or until the tops turn golden-brown and a toothpick inserted in the middle of the cupcake comes out clean.
Allow cupcakes to cool completely before frosting. Garnish with chopped pecans.
Notes
You can absolutely use all-purpose flour in place of the cake flour, the crumb of your cupcakes will just be a little heavier in texture.
Store leftover cupcakes in the refrigerator for up to 3 days. Allow cupcakes to come to room temperature before serving.
Freeze unfrosted cupcakes for up to 3 months or frosted cupcakes for up to 1 month.