01 - Preheat oven to 350°F (175°C). Grease a 9x13-inch baking dish.
02 - In a large bowl, whisk together pumpkin purée, evaporated milk, eggs, granulated sugar, brown sugar, pumpkin pie spice, salt, and vanilla extract until smooth.
03 - Pour the pumpkin mixture into the prepared baking dish and spread evenly.
04 - Sprinkle the dry cake mix evenly over the pumpkin mixture.
05 - Drizzle the melted butter evenly over the cake mix, covering as much as possible.
06 - Sprinkle with chopped pecans if using.
07 - Bake for 45–50 minutes, or until the top is golden and a toothpick inserted into the center comes out mostly clean.
08 - Allow to cool for at least 20 minutes before serving. Serve warm or at room temperature, optionally with whipped cream or vanilla ice cream.