01 - Preheat oven to 350°F. Lightly grease a 9x13-inch baking pan to prevent sticking.
02 - In a large bowl, whisk together pumpkin puree, sweetened condensed milk, eggs, pumpkin pie spice, sugar, and salt until fully blended.
03 - Transfer the pumpkin mixture into the prepared baking pan, spreading the surface evenly.
04 - Sprinkle the dry yellow cake mix evenly over the pumpkin mixture, taking care not to stir.
05 - Drizzle melted butter evenly over the dry cake mix, covering as much as possible. Distribute chopped pecans across the top if using.
06 - Bake in the preheated oven for 45 to 55 minutes until the surface is golden and the center no longer jiggles. The dessert will set further as it cools.
07 - Allow to cool for at least 30 minutes before slicing. Serve warm or chilled as desired, optionally accompanied by whipped cream or vanilla ice cream.