Preheat oven to 180°C. Grease a regular loaf pan (refer to notes regarding pan size) with butter and line with parchment paper.
Mash overripe bananas in bowl until fine, set aside.
Sift flour & baking powder. Set aside.
Add eggs into bowl of a stand mixer. Beat on medium speed for 1 min and then increase to the highest speed for another 2 min. The egg should become bubbly. Add sugar & beat on the highest speed for 3 mins. The mixture should be foamy.
Add in mashed bananas and gently stir 2-3 times with a spatula to combine.
Add ½ the butter into egg mixture, gently fold and stir 2-3 times.
Next add ⅓ of the flour, gently fold and stir until just incorporated.
Add in another ⅓ of the flour, stir gently to incorporate.
Add the remaining ½ butter, gently stir to mix and finally add the remaining ⅓ of flour. Gently stir and make sure the flour is fully dissolve but be sure n͟o͟ ͟t͟ to over mix. Ensure batter retains air bubbles in the beaten eggs.
Pour cake batter into the pan and bake for 30-35mins, or until a cake tester comes out clean in the center. If top of the cake is browning too much, cover with aluminum foil after the cake is set at the top, about 20-25 mins into baking.
Remove cake from oven, let cool on a wire rack for 10 mins then slice and enjoy!