Preheat the oven at 350 F and line an 8-inch cake pan.
In a bowl, whisk flour, sugar, baking powder and salt together.
Mash bananas into puree. Then add it into the wet ingredients bowl with vanilla and milk. Whisk until well combined. Divide the batter in half. Add cacao powder in one half and whisk to combine until smooth and chocolate colored.
In the cake pan, pour a bit of white batter, then the chocolate batter, alternating. Repeat until no more batter.
Bake for 45 to 50 minutes or until a toothpick comes out clean when inserted in the middle.
Remove from the oven and let cool down completely.
Decorate and enjoy!
