Prepare cake mixes together as directed on package; bake in two 8 in. (20 cm) round pans, with their sides greased and the bottoms lined with wax paper.
Allow to cool.
Meanwhile, prepare butterscotch pudding as directed on package.
Allow to partially set; then stir in nondairy whipped topping.
Place one cake upside down on a cake plate or platter.
Frost with a thin layer of pudding topping.
Cut each banana into very thin slices.
Place one of the sliced bananas between the layers.
Add the top cake layer, and frost the top and sides of the cake with pudding topping.
Decorate top with remaining banana slices.