Preheat the oven to 350°F (175°C). Line a 9x5 inch loaf pan with parchment paper.
In a small bowl, combine the flour, baking powder, cinnamon, and salt. Whisk together until well blended.
In a large mixing bowl, combine the mashed bananas with brown sugar until just mixed. Slowly add in the oil while whisking gently, then add eggs and vanilla extract.
Add the dry ingredients mixture into the wet ingredients gradually while whisking gently just until combined. Fold in chopped banana pieces.
If desired, combine sugar and cinnamon for a topping mixture; pour batter into prepared pan and top with halved banana before sprinkling with cinnamon sugar. Bake for about 55-65 minutes.
Once baked, cool in the pan for about 15 minutes before transferring to a wire rack to cool completely.