Heat your oven to 350 degrees F or 180 degrees C.

Put the flour and salt in a bowl. Sift in the baking powder and baking soda to avoid any lumps. Add the cocoa powder. Mix well. Add the sugar and mix.

Whisk the eggs, add the oil and combine. Add the mashed bananas and vanilla extract. Whisk until smooth. Make a well in the center of the dry ingredients and pour in the wet ingredients. Stir until smooth. Add boiling water or coffee little by little until smooth.

Bake in the heated oven for approximately 35 minutes. Definitely check at 30 minutes if your oven runs hot. The cake is done when a toothpick inserted into the middle comes out clean or with very few crumbs. Cool the cake completely on a wire rack.

Frosting - put softened butter in a mixer bowl. Cream the butter for a minute. Sift in the cocoa powder. Beat that for a minute. Add a little milk and vanilla extract. Then add powdered sugar a little bit at a time. Keep adding milk as needed. Beat this for a few minutes until fluffy. You can add more or less sugar depending on your taste. When the cake is cool, cover it with the creamy frosting.