Moist Banana Nut Bread

½ cup salted butter

1 cup granulated sugar

2 large eggs

½ cup sour cream , or plain Greek yogurt

1 ½ teaspoons vanilla extract

2 cups all-purpose flour

1 teaspoon baking soda

¾ teaspoon fine sea salt

2 cups mashed very ripe bananas

¾ cup chopped walnuts