1Cream together butter and sugar until fluffy, add eggs, one at a time, then vanilla. Add sifted dry ingredients to creamed mixture ALTERNATELY with sour cream, scraping bowl periodically. Add mashed bananas, JUST UNTIL BLENDED.
Pour into greased and floured pan, bake for APPROXIMATELY 30 MINUTES ( my oven runs hot so I check sooner), checking with a toothpick for doneness.
If you want to use a frosting with this cake, I would recommend a Cream Cheese Frosting, using 1 8 oz. of cream cheese and slightly more than one cup of powdered sugar with a teaspoon of vanilla.