Dump the cake mix and pumpkin puree into a large bowl.
Stir the muffin batter. A few dry spots or lumps are fine but still try to get the batter as even-looking as possible.
Using a ½ cup measuring cup, portion the pumpkin spice muffin batter into a pre-lined jumbo muffin pan.
Bake for 18 to 25 minutes (depending on how big your muffins are) until an inserted toothpick comes out clean.
Cool on a cooling rack, and then enjoy!
Notes
Watch out when you are at the grocery store that you buy pure pumpkin puree and not canned pumpkin pie filling.
A measuring cup, cookie scoop, or ice cream scoop makes portioning muffins into muffin cups an easy task.
Oven temperatures vary and may need to be recalibrated periodically to ensure they are accurate. Make sure to check your muffins at the lower end of the recommended baking time.