BTW, my sister-in-law cooks salmon this way (with the layers of onions). She wraps it (the fish and onions) in foil, which is so much easier to clean! She also makes a white sauce to go on top, which is so yummy. But we find that the tilapia is flavourful enough that we don't need the sauce (again, watching the cholesterol!)
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When you don't like a thing, change it.
If you can't change it, change the way you think about it.

(Maya Angelou)