Preheat the oven at 170ºC conventional oven and prepare a 20x20 cm baking pan with parchment paper.
Stir all-purpose flour, baking soda, baking powder and salt together in a bowl.
175 g all-purpose flour, ½ teaspoon baking powder, ¾ teaspoon baking soda, ½ teaspoon salt
Mash the bananas and set it aside. Mix together milk and vanilla extract and set it aside.
180 g very ripe bananas, 75 g full-fat milk, ½ teaspoon vanilla extract
Add the butter and granulated sugar in a bowl and whisk it together with a strand mixer or with an electric hand-mixer. Whisk on high speed, for 2-3 minute so it becomes light and airy
125 g granulated sugar, 60 g butter
At low speed, add the eggs one at a time until they are incorporated into the batter.
2 eggs
Continue on a low speed, and add ⅓ of the flour mixture and mix it in. Then add the mashed banana and mix it in. Add another ⅓ of the flour mixture and mix it in. Add the milk/vanilla and mix it in. Finally add the last ⅓ of the flour mixture and mix until just combined. Be careful to not over mix.
Use a spatula, and give the batter a final mix, making sure everything has been combined.
Add the cake batter into the prepared baking tin and bake them for 28-30 minutes or until a cake tester comes out clean.
Let the cake cool on a cooling rack. After 5-10 minutes, gently remove the cake from the cake tins and let it cool down completely.