Slice the ripe bananas into bite-sized pieces and place them in a large mixing bowl. Add the drained crushed pineapple and fresh strawberries, mixing gently to combine.
Spread the fruit mixture evenly across the bottom of a greased 9x13 inch baking pan.
Evenly sprinkle the dry cake mix over the fruit layer without mixing.
Drizzle the melted unsalted butter over the top of the cake mix layer.
Preheat your oven to 350°F (175°C) and bake for about 40 minutes or until golden brown on top.
Allow the dump cake to cool slightly before adding toppings. Whip up one cup of heavy whipping cream until soft peaks form if using that instead of whipped topping.
Serve generous portions topped with whipped cream, extra sliced bananas, fresh strawberries, and a sprinkle of chopped nuts.