Preheat oven to 350 degree Fahrenheit.

Place the yellow cake mix in a large bowl.

Add the bananas also the bowl, mash the bananas, small chunks of bananas are totally fine!

Add melted butter (or oil) and vanilla extract (if using), mix everything together until the ingredients are evenly combined.

Pour spoonfuls of batter on to prepared muffin moulds, bake in the preheated oven for about 18 minutes. Then, increase the heat to 375 degree Fahreanheit and bake for another 12 to 15 minutes ( about 30 to 35 minutes baking in total) until a toothpick inserted at the center of the muffins come out cleaner so you know the muffins are fully cooked on the inside!

In case the top gets browned before the inside is completely cooked, you can loosely cover the top of the muffin pan using an aluminium foil and bake which will prevent the further browning of the top, while the inside will continue to cook. However, if you do this, make sure to remove the foil for the last couple of minutes of baking so the top won't look soggy!

Once the muffins are fully baked, transfer the muffin pan to a cool place. Allow the muffins to cool down for a few minutes, serve them while they are still warm for the best results! Serve the delicious cake mix banana muffins with a cup of milk or tea or coffee as you wish!