So let's imagine...

[CustardLover]

You made a polenta and orange upside down cake in a springform tin, without lining the bottom of your oven; what the feck would you do to clean the caramel off it? Help!

[wowfudge]

Hot water and a cloth - best while the oven is still warm. As it won't be now, just a cloth wrung out in very hot water - get some rubber gloves on - and rub, rub, rub.

[squiggletea]

Agree with above. Lots of soapy water and while warm.

DBIL did this to our oven with a pineapple upside down cake with extra brown sugar . I managed to do the cleanup while he took the chef's credit!!

[OopsDearyMe]

Bicarb and lemon juice?