Preheat oven to 325°F and spray a 9x5 loaf pan with non-stick spray. Set aside.
In a large bowl, mash banana to remove as many of the lumps as possible. If desired, run through a food processor or blender for a couple seconds.
Add eggs, buttermilk, butter or oil, vanilla and whisk until well combined.
Add brown sugar and whisk again until well combined.
Add flour, baking soda and salt and whisk until just combined.
Pour batter into prepared pan and bake on rack in the lower third of the oven for 60 minutes, or until a toothpick inserted into the middle comes out clean.
Leaving loaf in the pan, place on wire rack to cool for 15-20 minutes. Invert and carefully remove loaf and place back on wire rack to cool completely.
Slice into 8 pieces and enjoy!