Butter a 13x9-inch baking dish. Place the bread cubes in the dish, pour melted butter over it, and toss.
In a large bowl, whisk together milk, cream, sugar, yolks, eggs, pumpkin puree, vanilla, pumpkin spice, and salt. Pour mixture over bread cubes. Let stand for 20 minutes, toss occasionally.
Preheat oven to 350°F. Sprinkle turbinado sugar over bread pudding. Place in the oven and bake for 50 minutes or until golden brown and set center. Remove from oven and cool for 30 minutes. Serve warm.