Preheat your oven to 350°F (175°C). This ensures that your banana bread bakes evenly.
Grease your loaf pan with butter or cooking spray to prevent the banana bread from sticking.
In a large mixing bowl, combine the melted butter and granulated sugar. Mix until well combined. Then, add the eggs, vanilla extract, and sour cream, stirring until smooth.
In a separate bowl, mash the ripe bananas with a fork or a potato masher until smooth. You want a nice banana puree with minimal lumps.
Add the mashed bananas to the wet mixture, stirring to combine. In another bowl, whisk together the flour, baking soda, salt, cinnamon, and nutmeg (if using). Gradually add the dry ingredients to the wet mixture, folding gently until just combined. Be careful not to overmix!
Pour the batter into the prepared loaf pan and smooth the top. Bake in the preheated oven for 60-70 minutes, or until a toothpick inserted into the center comes out clean.
Once baked, remove the loaf from the oven and let it cool in the pan for about 10 minutes. Then, transfer it to a wire rack to cool completely before slicing. Enjoy your Banana Bread warm or at room temperature!