Prepare a 9x5 loaf pan by spraying with cooking spray. Preheat oven to 325℉.
Add flour, baking soda, salt and cinnamon to a bowl and whisk until combined.
In another bowl, add the egg, sugar, and oil and mix until combined.
In a separate small bowl, mash the bananas using a fork.
Slowly add the dry ingredients to the wet, mixing well until all combined. The mixture will be dry and crumbly.
Add the buttermilk, vanilla and bananas. Mix until combined.
Fold 3/4 of the pecans into the mixture.
Pour the mixture into prepared pan. Sprinkle the remaining pecans on top.
Bake for 1 hour or until a toothpick inserted in the center comes out clean.