To make cake: whisk together dry ingredients (flour - salt) in a medium bowl.
In a seperate bowl whisk together remaining cake ingredients (banana - vanilla).
Gradually add wet mixture to dry, stirring until blended.
Pour batter into pan (9x13 sprayed with Pam) or into paper lined muffin tins (makes about 18 cupcakes). For cake bake 30-35 minutes; for cupcakes bake for 20-25 minutes or until toothpick in center comes out clean. Remove to cooling rack and let cool.
For frosting: in a medium bowl and and electric mixer on high speed, beat all frosting ingredients until smooth and then with a spatula frost cake or cupcakes.