Preheat oven to 350 degrees F (175 degrees C). Grease a 9x5 inch loaf pan. My personal preference is lining the pan with parchment paper for easier removal!
In a large bowl, stir together the melted butter and sugar.
Add the eggs and vanilla, mix well.
Combine the flour, baking soda and salt, stir into the butter mixture until smooth.
Finally, fold in the sour cream, walnuts and bananas.
Spread evenly into the prepared pan.
Bake at 350 degrees F (175 degrees C) for 60 minutes, or until a toothpick inserted into the center of the loaf comes out clean.
Let cool for about 30 minutes, preferably longer.
Loosen loaf around sides and flip onto a cooking rack or serving tray to cool completely. Or lift out of the pan by holding onto parchment paper. (You can even refrigerate it for a while to make sure it's set!)