Whisk the flour, baking soda, salt, and cinnamon together in a large bowl and set aside.
In the bowl of a stand mixer fitted with a paddle attachment, cream together the butter and brown sugar on medium-high speed until light and fluffy.
Decrease the speed to medium and add the eggs one at a time, beating well after each addition.
Beat in the sour cream, mashed bananas, and vanilla extract on medium speed until combined.
With the mixer running on low speed, slowly add the dry ingredients, and mix until just incorporated. Fold in the pecans using a silicone spatula.
Pour the batter into the prepared loaf pan and bake for 60-65 minutes or until a toothpick inserted in the center of the loaf comes out clean. Cover the loaf with aluminum foil if it starts to brown before the center is fully cooked.
Remove the banana bread from the oven and allow the bread to cool for 15 minutes before turning the loaf out and allowing to cool completely to room temperature.