Preheat oven to 350°. Line a 9x13” pan with foil and spray with cooking spray.
Mix cake mix, pumpkin, oil, eggs, and pumpkin pie spice in a large bowl with a hand mixer until well incorporated, about 2 minutes. Reserve 1/2 cup of batter and place the rest into the prepared pan.
Place reserved batter back into your bowl, and and add the melted butter and cinnamon. Stir to combine.
Place dollops of the cinnamon batter mixture over the cake and swirl with the back of a wooden spoon.
Bake for 23-25 minutes, until a toothpick comes out clean. Cool completely.