My family always made rhubarb upside down cake. My mom uses a white cake mix,brown sugar, and I think some white sugar also.
Make the cake as the box calls for it.
Cut the rhubarb into pieces.
Grease or oil your pan as the box says.
Put the rhubarb on the bottom, then some brown sugar and some white sugar.
Then pour your cake mix over the rhubarb. And cook as
directed.
Let it cool and add cool whip or pour milk over it and enjoy.
It may not sound like milk would be good over it but I think it is good. I also put milk over my chocolate cake.
I will check with my mom I do believe you use both sugars not very much mind you. But I want to make sure I am giving you the correct directions. I think I will be getting some rhubard this weekend. That sounds so good.