Preheat the oven to 350°F (175°C). Grease a 9x13 inch baking dish or line it with parchment paper for easy removal.
In a large bowl, whisk together pumpkin puree, evaporated milk, eggs, both sugars, pumpkin spice, and salt until smooth and well combined.
Pour the pumpkin mixture into the prepared pan and spread it evenly. Sprinkle the dry cake mix evenly over the top. Do not stir!
Drizzle melted butter evenly over the dry cake mix. Sprinkle pecans all across the top.
Bake for 50-60 minutes, or until the top is golden brown and the center is set. A toothpick inserted in the center should come out clean.
Let the cake cool for at least 20-30 minutes before slicing. Serve warm, at room temperature, or chilled. Top with whipped cream or a scoop of vanilla ice cream. You can even sprinkle a little bit of cinnamon over the top of the ice cream or whipped cream.