In a bowl whisk together the flour, baking powder, baking soda, all spice cinnamon and salt, and set aside.
In a separate medium sized bowl, whisk together the brown sugar and oil until well combined. (Whisk by hand for about 2 minutes)
Add the vanilla extract and buttermilk to the oil and sugar mixture and mix well or until the sugar is dissolved (about 2 minutes)
Gently fold in the dry ingredients and mix until everything is well combined and there are no large flour pockets in the batter. Do not over mix at this stage.
Fold in the soaked fruit (include any liquid left in the pot) into the batter (see note 7)
If using any peanuts, almonds or cashew nuts, you can mix it into the batter now.
Transfer the batter to the prepared cake pan.