Preheat oven to 350 degrees F. Spray a 9x12 pan with a Pam cooking spray. Make the brownie mix as directed and set off to the side. Do the same with the cake mix.
Pour 1/4 of brownie mix into pan. Pour 1/4 of the cake mix into the pan on top of the brownie mix. Repeat until both batters are gone. After completed, take a fork and swirl the batters slowly in a side to side formation. Then add a pinch of cinnamon to the mix and mix one more time.