In a large mixing bowl, add the cake mix. Then pour in the melted butter, pumpkin and cinnamon. Stir to fully combine. It will be pretty thick, almost more like cookie dough.
Line a 11x7 inch baking dish with parchment paper.
Then press the batter evenly into the baking dish and set aside.
Now, make the topping. In a large mixing bowl or the bowl of a stand mixer, add the vegan cream cheese. Using a hand mixer or the paddle attachment for the stand mixer, beat the cream cheese until smooth.
Add the melted butter and continue to beat together until fully combined, scraping down the sides as needed.
Then add the pumpkin and vanilla. Continue to mix together until combined.
Add the cinnamon, nutmeg, salt and corn starch. Mix together.
Next, add the powdered sugar a little at a time, until completely incorporated. Scrape down the sides and make sure everything is fully combined.
It will be very liquidy, so just pour it on top of the cake batter already in the pan. Smooth out evenly.
Bake for 40-45 minutes the sides of the top should look like they are getting a little firm, but the center will still look very jiggly and almost liquidy. Don't worry, it will firm as it chills.
Cool completely, then put in the fridge for at least 6-8 hours, but overnight is better. Keep chilled until ready to serve. Cut into squares and serve with vegan whipped cream or extra powdered sugar.
Notes
*Duncan Hines is accidentally vegan and not certified. Most of them are vegan, but check the package to make sure if you are picking the right one. There are many certified vegan cake mixes if you prefer that!