Peel the banana and cut it into small pieces. If using a very ripe banana, it should be soft enough to mash easily.
In a medium-sized pan, add the banana pieces and water. Cook over medium heat, stirring occasionally until the banana softens and begins to break down (about 5 minutes).
Once the banana is soft, add the grated coconut, sugar, cardamom powder, cinnamon powder (if using), and a pinch of salt.
Continue to cook the mixture, stirring frequently, until it thickens and the coconut is well combined with the banana (about 10 minutes).
When the mixture has reached a thick, spreadable consistency, remove it from the heat.
Allow the Banbukeylu Harisa to cool completely before serving.
Enjoy your meal!