Spray the inside of the slow cooker with nonstick cooking spray.
Whisk pumpkin, eggs, evaporated milk, sugar, pumpkin pie spice, and salt in a bowl until smooth.
Pour pumpkin mixture into the slow cooker and spread evenly.
Sprinkle dry cake mix evenly over the pumpkin layer. Do not stir.
Lay thin slices of butter across the cake mix, covering as much surface as possible.
Cover and cook on High for 2 to 2 1/2 hours or Low for 3 1/2 to 4 hours, until set.
During the last 30 minutes, prop the lid slightly open with a wooden spoon handle to release steam.
Serve warm with whipped cream or ice cream.
Notes
Spray the slow cooker well because pumpkin dump cake sticks. Do not stir the dry cake mix into the pumpkin layer; the separate layers create the topping. A 6-quart slow cooker gives the best surface area. Refrigerate leftovers up to 4 days, but freezing is not recommended because the texture gets watery.
Keyword crock pot pumpkin dessert, pumpkin dump cake