Rhubarb cake turned my pan black!

[ewatkins]

I made the rhubarb cake that was on the BB for myself as a Mother's Day treat. It was very good! I put the rest covered in the fridge overnight. I just went to get a piece, and the places where the rhubarb touched the pan have turned black! I took the cake out of the pan, and it is not black -- can I eat it?
The pan was just an 8x8 shiny pan from the grocery store -I guess it's aluminum? I have cooked rhubarb before but didn't have this problem. I guess it's the pan? Any ideas on how to get it clean?

[Anne]

Hi ewatkins. The acid in the rhubarb reacted with the aluminum. This is the same thing that happens with tomatoes cooked in an aluminum stock pot. I would not eat the cake and would switch to a non-reactive pan. I like using glass cake pans for rhubarb but I think a pan lined with non-stick coating would also work.