Preheat oven to 350. Coat a 9×13 inch baking dish with cooking spray.
In a large bowl whisk together the pumpkin, eggs, heavy cream, milk, sugars, pumpkin pie spice and salt until well blended. Add the cubed challah and dried cranberries and stir to coat evenly with the pumpkin mixture.
Pour into the prepared dish and spread evenly. Pour the melted butter over the top evenly.
Bake for 35-40 minutes or until the center is set. Remove from the oven and allow to cool for about 5 to 10 minutes before serving. Dust with powdered sugar and serve.