Mash bananas and set aside. Sift flour with soda and baking powder and set aside. Cream butter, add sugar and beat until and fluffy. Add eggs, beating well after each addition. Mix buttermilk and vanilla into mashed bananas. Alternately add flour mixture and banana mixture to the creamed butter, sugar and eggs. Beat until smooth and well blended. Do not overmix. Divide equally into two 9 inch cake pans or one 9 x 13 pan, greased and floured. Bake in 375 degree oven for 25 to 30 minutes.

Icing: Cream butter and 1/3 box powdered sugar, add vanilla, salt, and milk. Blend add remaining powdered sugar.