1 ½ sticks cold unsalted butter, sliced into ⅛-inch-thick pats
Directions
Preheat the oven to 350 F. Lightly grease a 9×13-inch baking dish with butter or cooking spray.
In a large bowl, whisk together the pumpkin puree, sweetened condensed milk, and eggs until completely smooth.
Pour the pumpkin mixture into the prepared baking dish and spread it into an even layer.
Sprinkle the dry spice cake mix evenly over the pumpkin filling, making sure to cover the entire surface. Do not stir the cake mix into the filling.
Arrange the butter closely together over the cake mix, covering as much of the surface as possible.
Bake for 50 to 60 minutes, until the topping is golden brown and the pumpkin filling is set around the edges. The center may still have a slight jiggle.
Remove the cake from the oven and cool for at least 30 minutes before serving. The filling will continue to firm up as it cools.