Preheat your oven to 180°C. Line a 1.5-litre loaf pan with parchment paper.
In a large mixing bowl, mash the ripe bananas with a fork until smooth.
Add the melted butter, white and brown sugar. Combine the ingredients using a whisk until the sugar is dissolved. If you prefer the banana cake to be on the sweeter side, you can increase the amount of sugar mentioned in this recipe.
Add in the eggs, one at a time, until well combined. Add the milk and vanilla extract.
Whisk together the flour, baking powder, baking soda, cinnamon powder and salt in a separate bowl. Sift the ingredients.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Be careful not to overmix.
Add the finely chopped walnuts and gently fold them evenly into the batter.
Pour the batter into the prepared loaf pan and spread it evenly.
Bake in the preheated oven for 45-50 minutes, or until a toothpick inserted into the centre of the cake comes out clean.
Remove the cake from the oven and let it cool in the pan for about 10 minutes. Then, transfer it to a wire rack to cool completely.
Once cooled, slice and serve your delicious banana cake. Enjoy!