Preheat the oven to 350°F. Spray 9 x 13-inch baking dish with baker's spray. Set aside.
In a large mixing bowl, whisk together by hand the pure pumpkin puree, eggs, evaporated milk, granulated sugar, vanilla extract, pumpkin pie spice blend, and cinnamon until smooth and all the ingredients are fully incorporated.
Pour the pumpkin filling into the prepared baking dish and spread it into an even layer.
In a medium bowl, stir together the dry spice mix and chopped pecans. Sprinkle the spice cake mix evenly over the top of the pumpkin filling.
In a medium bowl, stir together the melted butter and whole milk.
Slowly pour the butter and milk mixture over the top of the entire dry cake mix layer. Make sure that no large dry pockets of spiced cake mix are showing. If they are, take a spoon and gently push the dry mix under the butter being careful not to stir the butter and cake mix, but just submerge the cake mix under the butter. A few small little spots of dry mix showing are ok but you really want as much of the dry mix submerged under the butter and milk mixture.
Bake for 1 hour or until the top is golden and the center has set.