Preheat the oven to 350 degrees.
Add the melted butter and sugar to the mixing bowl and mix for 2-3 minutes.
Peel the bananas and break them into several chunks. Add the bananas, eggs, sour cream, and vanilla to the creamed butter and sugar.
Mix the wet ingredients until the batter is well mixed. Note: There may still be small chunks of mashed bananas in the batter.
Add the flour, baking soda, and salt to the batter. Mix on low speed just until dry ingredients are incorporated. It's important to not over mix.
Prepare the bread pan by rubbing all the sides and bottom of the pan with butter. Then sprinkle the butter with flour, dump out any excess flour that isn't sticking. Note: Only a light layer of butter and flour is needed to prevent the banana bread from sticking.
Pour the batter into the prepared bread pan. Use the spatula to scrape all of the batter out.
Bake the banana bread for 50-60 minutes.
The banana bread will be done when the sides and top of the loaf is a nice golden to dark brown. Place a toothpick into the top and remove it, if there is any batter on the toothpick continue to bake it for another 3-5 minutes.
Place the bread pan on a wire rack and allow it to cool for 5-10 minutes.
Then remove the bread by running a knife between the edge of the banana bread and pan. Turn the bread pan over and the banana bread will fall out. Slice and enjoy!