Preheat oven to 350°F. Lightly grease a 9x13-inch baking dish.
Add the bananas directly to the baking dish and mash well with a fork.
Add the brown sugar, maple syrup, Watkins Baking Vanilla, Watkins Cinnamon, nutmeg, and salt. Stir everything together directly in the baking dish, then spread into an even layer.
Sprinkle the dry butter pecan cake mix evenly over the banana mixture. Do not stir.
Sprinkle the chopped pecans evenly over the cake mix.
Slice the cold butter as thinly as possible and arrange the slices over the entire top, covering as much of the dry cake mix as possible.
Bake for 40–50 minutes, or until the top is golden brown and crisp and the banana mixture is bubbling around the edges.
If you notice any dry cake mix spots near the end of baking, add a small piece of butter over those areas and return to the oven until golden.
Allow the dump cake to rest for 10–15 minutes before serving.
Serve warm on its own or with a scoop of vanilla ice cream and a drizzle of maple syrup.