I was testing out a gluten free mix and wondered if I could use pumpkin as a swap. I used a 20 oz gluten free mix, added nothing but 2 small cans of pure pumpkin puree (NOT pumpkin pie mix)... and baked it (at 325F) for the same time as the box called for with an 8 x 8 pan.. for about 45 minutes.
Put them in the fridge after they cool down and wait over-night.
This yielded very fudge-like 'brownies.' I hate pumpkin, but you cannot taste the pumpkin. --I definitely recommend trying this variation if you need brownies for a birthday or a holiday. The good part is that they are very rich (so at least for me they are impossible to over-eat: eat 1 and you're done).
NOTE: I post this because I have tried swapping 1 can of pumpkin with a GF mix, and it was too dry. However 2 cans seems to do the trick.