I put parchment on the bottom of the pan (cut to size for my 9" cake pan) and cut a strip to fit around the edge, so all surfaces were covered. I let the cake cool for about 10 mins before turning it out.Your idea came thru 16 minutes before I read it.
I am going to make such a cake. Yes,, The oranges will be peeled, since the poster mentioned the bitterness.
Now I still have a question.
I never made an Upside-down cake. How do you remove from baking pan without it falling apart???
I was considering lining pan with parchment. I mainly use steel pans. Used Pyrex bowls,,, but only when I bake Flan.
Silicone pans are nothing I want to consider.
Good luck with your cake.

