01 - Preheat the oven to 350°F. Lightly grease a 9x13-inch baking pan.
02 - In a large mixing bowl, whisk together the pumpkin puree, sweetened condensed milk, eggs, pumpkin pie spice, granulated sugar, and salt until smooth and fully blended.
03 - Pour the pumpkin mixture into the prepared baking pan and spread it evenly with a spatula.
04 - Sprinkle the dry yellow cake mix in an even layer over the pumpkin mixture, ensuring complete coverage and without stirring.
05 - Drizzle the melted butter evenly over the cake mix layer, coating as much of the surface as possible.
06 - Distribute chopped pecans evenly across the top if using.
07 - Bake for 45 to 55 minutes, until the surface is golden brown and the center is set. The dessert will firm up further as it cools.
08 - Allow to cool in the pan for at least 30 minutes before serving. Serve warm or chilled, with whipped cream or vanilla ice cream if desired.