Add the pumpkin, cinnamon, ginger, cloves, nutmeg, milk, vanilla extract, maple syrup, and eggs to a large bowl and whisk to combine.
Pour the pumpkin mixture into a 9×13-inch baking dish, then pour the yellow cake mix over top in an even layer. Sprinkle the pumpkin spice over top.
Layer the slices of butter on top of the cake mixture, then bake for 45 minutes. After 45 minutes, pour the pecans on top of the cake, then return to the oven and bake for an additional 15 minutes, until the cake is browned and crisp.
Let cool slightly, then serve warm. Top with vanilla ice cream or whipped cream, if desired.
To make this cake dairy-free, substitute full-fat coconut milk for the milk in the pumpkin filling, and top with ghee or your favorite vegan butter substitute.