Preheat your oven to 350°F (175°C). Grease a 9x13-inch baking dish.
In a large mixing bowl, combine the pumpkin puree, evaporated milk, eggs, sugar, cinnamon, nutmeg, ginger, and salt. Whisk until smooth and well combined.
Pour the pumpkin mixture into the prepared baking dish, spreading it evenly.
Sprinkle the dry cake mix evenly over the pumpkin mixture. Do not stir.
If using, sprinkle the chopped nuts over the cake mix.
Drizzle the melted butter evenly over the top.
Bake for 50-60 minutes, or until the top is golden brown and a toothpick inserted in the center comes out clean.
Allow the cake to cool for at least 15 minutes before serving. Serve warm or at room temperature, optionally topped with whipped cream or vanilla ice cream.