I hit on a winner last night.  Even the picky girl liked it.  She went back for thirds, even, which pretty much never happens with her unless dinner consists of mac & cheese or snickers bars.

On a large piece on tinfoil, I laid down a thick layer of baby spinach leaves, and on top of that sliced tomato.

Next came a couple of mahi mahi fillets from Trader Joe's (where the prices for frozen fish are super-reasonable).  On top of the fish I sprinkled some red Hawaiian salt, and about half a can of thick coconut milk.  Chopped onions over the whole thing. 

Sealed it up in foil, and baked at 375° for around 40 minutes.  After it came out of the oven, I topped it with sliced avocado.  Served up with some fried rice with Chinese sausage and sugar snap peas. 

Totally a meal I'd do again, especially after the kid's reaction.