How to tell the difference when grouping with と and marking a possessive with の?

I found this book for my wife, and I thought it meant "The sheep and the forest of steel", but she corrected me and said it's actually "The forest of sheeps and steel", and I should've gotten a clue by the cover (I just glanced at the title).

But how would one be able to tell the difference? I cannot think of an actual example, but let's say someone tells me "ブルーベリーとニンジンのケーキを持ってきて". Should I bring "blueberries and a carrot cake" or "a blueberry and carrot cake"?

I mean, now I realise I should ask them to specify, but prior to this I probably would've brought two items.