Preheat oven to 350 degrees. Line an 8x8 baking pan with parchment paper.
In a stand mixer, cream together beat the butter, brown sugar until light and fluffy.
Add the eggs, and vanilla with the paddle attachment until well blended.
dd the dry ingredients to a medium bowl--flour, baking soda, salt, and spices. Whisk to combine.
Add the dry ingredients to the wet ingredients and mix until just combined.
Pour the batter into the prepared pan, and smooth until level.
Lay the remaining 1.5 banana (3 lengthwise slices) into the top of the batter.
Sprinkle the top with turbinado sugar.
Bake for 45-50 minutes until a toothpick can be removed from the center without wet batter.
Cool and serve.
