Preheat oven to 350 degrees. Spray a 9 X 13" baking dish with cooking spray.
Mix the dry cake ingredients well in a large bowl. Add in the oil, eggs and vanilla. Mix well.
Stir in the bananas, nuts and pineapple. Mix well.
Pour batter into the baking dish and bake for about 30-35 minutes until a toothpick comes out clean from the center.
Allow cake to cool completely.
Frosting
Beat cream cheese and butter together with electric mixer. Beat in sugar and vanilla.
You can spread the frosting uniformly over the slab cake with an offset spatula.
If you choose to pipe the dressing it will not cover the entire cake so make a lattice pattern so you can cut between the frosting rows and each piece will have some frosting florettes.