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