Preheat the Oven: Preheat your oven to 350°F (175°C). Grease and flour a 9x5-inch loaf pan.
Mash the Bananas: In a large bowl, mash the bananas with a fork until smooth, leaving some small chunks if you prefer.
Cream the Butter and Sugar: In another bowl, cream together the softened butter and brown sugar until light and fluffy.
Add the Eggs and Vanilla: Beat in the eggs one at a time, ensuring each is fully incorporated before adding the next. Stir in the vanilla extract and dark rum if using.
Combine Dry Ingredients: In a separate bowl, whisk together the flour, baking soda, salt, cinnamon, and nutmeg.
Mix Wet and Dry Ingredients: Gradually add the dry ingredients to the wet mixture, stirring gently until just combined. Do not overmix.
Pour the Batter into the Pan: Pour the batter into the prepared loaf pan and smooth the top with a spatula.
Bake the Banana Bread: Bake for 55-60 minutes or until a toothpick inserted into the center comes out clean.
Cool the Bread: Allow the bread to cool in the pan for 10 minutes before transferring it to a wire rack to cool completely.