In mixer, use large mixing bowl. Beat butter, sugar, and eggs. Add milk, baking powder, baking soda, vanilla. Add mashed bananas and flour. Beat until smooth (about 3 minutes).
Pour batter in a greased and floured long cake pan (13 x 9 x 2). Bake at 375 degrees for 30-35 minutes. Test with toothpick for doneness. If toothpick comes out clean, it's done. If not, bake a few more minutes and retest.
Use the following recipe for the icing after cooling: