01 - Preheat oven to 350°F. Grease a 9x13-inch baking pan thoroughly with butter or nonstick spray.
02 - In a large mixing bowl, whisk together pumpkin puree, sweetened condensed milk, eggs, pumpkin pie spice, granulated sugar, and salt until mixture is smooth and homogenous.
03 - Pour the pumpkin mixture into the greased baking pan and spread evenly to cover the bottom.
04 - Distribute dry yellow cake mix evenly over the pumpkin layer, ensuring full coverage. Do not mix.
05 - Drizzle melted butter slowly and evenly over the cake mix, aiming to cover most of the dry surface. Sprinkle chopped pecans on top if using.
06 - Bake for 45 to 55 minutes, or until the surface turns golden brown and the center feels set when gently shaken. The dessert will firm up further as it cools.
07 - Allow the dessert to cool for at least 30 minutes before slicing. Serve warm or chilled, optionally garnished with whipped cream or vanilla ice cream.