Preheat oven to 350°, spray a 13 x 9 baking dish with a non stick spray. Set aside.
In a medium mixing bowl, whisk together flour, baking soda, baking powder, salt and sugar.
Add butter. Mix on low speed.
Pour buttermilk into dry mixture. Add mashed bananas. Continue to mix on low speed for 3 minutes until mixture is creamy.
Add eggs, mixing after each egg.
Pour into prepared baking dish.
Bake for 30-35 minutes or until tooth pick inserted comes out clean.
Poke holes all over top of cake with end of wooden spoon.
Let cake cool before covering cake with pudding.