Preheat oven to 350 degrees F. Spray a 13x9-inch baking pan with nonstick cooking spray. Set aside.
Puree bananas in a blender or roof processor to make 1 cup
Whisk together flour, sugar, baking soda, salt and cinnamon in a large bowl. Stir in bananas, pineapple with juice, eggs, oil and vanilla until well blended. Stir in cherries, nuts and chocolate chips.
Pour into a greased and floured 13x9-inch baking pan. Bake at 350 degrees 30 to 35 minutes, or until a toothpick inserted into the center of the cake comes out clean, with just a few moist crumbs. Cool 30 minutes before topping with creamy vanilla frosting (below).
Creamy Vanilla Frosting
Heat butter and milk until butter melts. Remove from heat and stir in powdered sugar and vanilla.
Beat until smooth.
Because of all the mix-ins inside these banana split bars, they can be a little tricky to cut. Chilling in the fridge for 20 minutes may make them easier to cut - just be sure to use a very sharp knife.
Sliced bananas on top for garnish are totally optional but look so pretty! To keep sliced bananas from turning brown, brush them all over with a little bit of citrus juice. I recommend having a little extra pineapple juice on hand for this since you're already using pineapple in the recipe. Lemon or orange juice would also work. An alternative would be to use crunchy banana chips on top.
Bananas not ripe enough? Cut a few slits in the peel and place them on a microwavable plate. Microwave for a minute or two until they turn dark brown. Handle with care (oven mitts are recommended) because they will be very hot. Let them cool 20-30 minutes before peeling and adding to your recipe.
This recipe makes about 15-36 bars, depending on how you cut them. For potlucks, I recommended cutting into at least 24 squares, but for an at-home dessert go big and cut 12-15 servings.
Make up to a day ahead of time. Cover and store in the fridge.