Preheat oven to 350°F. Grease a 9X5 in loaf pan.

In a large bowl, stir together melted butter and sugar. Add the eggs and vanilla, mix well. Combine flour, baking soda and salt, stir into butter mixture until smooth. Finally, fold in sour cream, walnuts and bananas. Spread evenly into prepared pan.

Bake at 350°F for 60 minutes, or until a toothpick comes out clean. Cool loaf in the pan for 20 minutes before removing to a wire rack to cool completely