Preheat the oven to 350°F (175°C). Grease and flour a 9×5-inch loaf pan.

In a large bowl, mash the ripe bananas. Stir in melted butter or oil, eggs, sugar, and vanilla extract until combined.

In a separate bowl, whisk together flour, baking soda, baking powder, salt, and cinnamon (if using).

Add dry ingredients to wet ingredients and stir until just combined. Fold in any optional mix-ins like nuts or chocolate chips.

Let the batter rest for 20–30 minutes, covered, at room temperature.

Pour the rested batter into the prepared loaf pan and bake for 50–60 minutes, or until a toothpick inserted into the center comes out clean.

Cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.