Heat oven to 350°F. Grease a 9x13-inch baking dish.
Whisk pumpkin, evaporated milk, both sugars, vanilla, pumpkin spice, and salt until smooth.
Spread the pumpkin mixture in the prepared dish.
Sprinkle dry cake mix evenly over the pumpkin layer. Do not stir.
Drizzle melted butter evenly over the surface. Scatter pecans on top.
Bake until the center is set and the top is deep golden, 50 to 55 minutes.
Cool 15 minutes before serving. Serve warm or at room temperature.