Preheat your oven to 350°F (175°C). Lightly grease a 9×13 inch baking dish.
In a large bowl, whisk together the canned pumpkin puree, evaporated milk, granulated sugar, and eggs. Pour this smooth mixture evenly into the prepared baking dish.
Sprinkle the dry yellow cake mix evenly over the pumpkin mixture. Do not stir it in.
Drizzle the melted unsalted butter over the dry cake mix. Distribute it as evenly as possible. Then, scatter the chopped pecans over the butter layer.
Place the dish in the preheated oven. Cook for 50-60 minutes, or until the top is golden brown and the center is set. Let it cool completely on a wire rack before serving.