Preheat oven to 350°F; grease a 9x5-inch loaf pan.
Whisk flour, baking soda, salt, and cinnamon.
Mix butter, sugar, eggs, vanilla, bananas, and sour cream.
Combine wet and dry ingredients; fold in walnuts.
Bake for 55-65 minutes; cool for 10 minutes in pan, then on rack.
Serve on a white ceramic platter with powdered sugar, cream cheese, and coffee.