01 - Preheat oven to 350°F. Grease a 9x13-inch baking pan 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 well blended.
03 - Pour the pumpkin mixture evenly into the prepared pan, smoothing the surface with a spatula.
04 - Sprinkle the dry yellow cake mix evenly over the entire pumpkin layer. Do not stir.
05 - Drizzle melted butter evenly over the surface of the cake mix, covering as much of the surface as possible.
06 - Scatter chopped pecans evenly over the top (if using).
07 - Bake for 45 to 55 minutes, until the top is golden brown and the center is set. The cake will firm up as it cools.
08 - Allow to cool for at least 30 minutes before serving. Serve warm or chilled, optionally topped with whipped cream or vanilla ice cream.