Preheat oven to 350°F (175°C). Grease a loaf pan or line with parchment paper.
Mash the bananas in a large bowl using a fork or potato masher until smooth with a few lumps.
Add the melted butter (or oil), eggs, and vanilla extract to the mashed bananas. Mix well.
In a separate bowl, sift the flour, baking powder, salt, and sugar together.
Gradually add the dry ingredients to the wet mixture, stirring gently until just combined.
If adding any optional ingredients like chocolate chips or nuts, fold them in now.
Pour the batter into the prepared loaf pan, spreading it evenly.
Bake for 50-60 minutes or until a toothpick inserted into the center comes out clean.
Allow the bread to cool in the pan for 10-15 minutes, then transfer it to a wire rack to cool completely.