Preheat oven to 350°F (175°C). Grease a 9x5-inch loaf pan or line it with parchment paper.
Mash bananas in a bowl until smooth (small lumps are okay).
Mix dry ingredients: In a separate bowl, whisk flour, baking soda, salt, and cinnamon.
Combine wet ingredients: In a large bowl, mix melted butter and sugar. Add eggs, vanilla, and mashed bananas. Stir well.
Fold dry into wet: Gradually add the dry ingredients to the wet mixture. Stir until just combined (do not overmix). Fold in nuts/chocolate if using.
Bake: Pour batter into the loaf pan. Bake for 55–60 minutes or until a toothpick inserted comes out clean.
Cool: Let it rest in the pan for 10 minutes, then transfer to a wire rack to cool completely.
