Preheat your oven to 350°F (175C/155C Fan). Grease and flour your baking pan. (see note)
Begin by creaming your sugars and butter together in a large bowl.
Add the eggs one at a time, mixing well after each addition.
In a separate bowl, sift together your dry ingredients - the flour, salt, cinnamon, ginger, nutmeg, baking soda and baking powder.
Add ⅓ of the dry ingredients to the cake batter. Mix until just incorporated.
Add the buttermilk and beat to combine.
Add in another ⅓ of the dry ingredients and beat until just combined.
Then add the banana, by breaking this into small pieces, and add the vanilla, beating to incorporate and break the banana down. (see note)
Finally add the last ⅓ of the flour and stir until just combined.
Pour into prepared pan and spread evenly.
Bake in the preheated oven for about 1 hour, checking for a skewer (inserted in the thickest part) to come out clean.
Remove from the oven and allow to cool for a couple of minutes in the baking tin, before flipping out onto a wire rack to cool completely.