How to turn a brownie mix into a cake? So, I asked my friend to get me a chocolate cake mix, but she accidentlt got me a brownie mix instead (Betty Crocker Brownie mix). I wanted to make a chocolate cake for tomorrow's Super Bowl. However, if there's no hope then I'll just make the brownies.

I can't turn them into cupcakes because I have no cupcake molds. I just have a rectangular pan. I also don't have baking powder. 

So the insturctions on the box say to add 1/4 cup of water, 1/4 vegetable oil, and 1 egg.

I've seen some sites that says to add one more egg. Would that really help? Has anyone converted a brownie mix into a cake?
Adding one more egg will give you more "cake like" brownies. 

If you have baking soda you could use that as leavening. If it were me I would add 1/4 tsp. baking soda to the dry mix and stir to combine. I would add additional liquid in the form of 1/4 cup of buttermilk or soured milk to activate the soda and use an extra egg. This should give you something that is more cake like, than brownie like.