01 - Preheat oven to 350°F. Grease a 9x13-inch baking pan thoroughly to prevent sticking.
02 - In a large mixing bowl, whisk together pumpkin puree, sweetened condensed milk, eggs, pumpkin pie spice, granulated sugar, and salt until smooth and fully blended.
03 - Transfer the pumpkin filling to the prepared baking pan, spreading it evenly over the base.
04 - Sprinkle the dry yellow cake mix evenly over the pumpkin layer without mixing.
05 - Drizzle melted unsalted butter evenly across the cake mix. Scatter chopped pecans on top if using.
06 - Bake in the center of the oven for 45 to 55 minutes, or until the topping is golden brown and the center is set.
07 - Remove from oven and allow to cool in the pan for at least 30 minutes. Serve warm or chilled, with optional whipped cream or vanilla ice cream.