Pre heat oven to 180°C or 160° Fan
Grease and line a loaf tin (I use a 24 x 13 cm tin)
In a jug, mash the bananas with a Bamix or stick blender and set aside
In the bowl of a stand mixer, cream the butter and sugar on medium speed for 3 minutes, until light and fluffy
Add the eggs, banana and vanilla, then mix until combined
In another bowl, combine the flour, salt, bi carb and spices. Add ⅓ of this to the mixer bowl and stir on low until just combined
Now add ½ of the buttermilk, mixing until just combined and continue alternating the ingredients.
Pour mixture into prepared pan and smooth the batter
If decorating with the extra banana, slice it in half lengthwise and place (cut side up) on top of the batter. Sprinkle with the extra brown sugar
Bake for 1 hour, until cooked through and golden
Rest in pan for 10 minutes, then turn onto a cake rack to cool completely before slicing.