01 - Preheat the oven to 350°F. Grease a 9x13-inch baking pan using butter or nonstick spray.
02 - Whisk together pumpkin puree, sweetened condensed milk, eggs, pumpkin pie spice, granulated sugar, and salt in a large mixing bowl until thoroughly blended.
03 - Pour the pumpkin mixture into the prepared baking pan and spread it into an even layer.
04 - Evenly sprinkle the dry yellow cake mix over the pumpkin layer without stirring.
05 - Drizzle the melted butter uniformly over the cake mix, covering as much surface as possible.
06 - Scatter chopped pecans over the surface, if desired, for a nutty finish.
07 - Transfer the pan to the oven and bake for 45 to 55 minutes until the top is golden brown and the center is set.
08 - Allow the dessert to cool in the pan for at least 30 minutes before serving. Serve warm or chilled, with whipped cream or vanilla ice cream if preferred.