Cream together butter and brown sugar. Add eggs one at a time, followed by vanilla and mix well.
In a separate bowl, whisk together flour, baking soda and salt. Add dry ingredients to the wet ingredients and mix well. Add banana and sour cream, and mix well.
Pour into a greased and floured loaf pan, smooth the top with a spatula and bake for 50-55 minutes , or until a toothpick inserted in the centre comes out clean. Let rest in pan on a rack for 10 minutes, then turn out onto rack to cool.
Recipe by Life at Cloverhill at https://lifeatcloverhill.com/2015/02/moist-delicious-banana-bread.html