The salt dome fish was something we did a few years back for another Christmas dinner with the family in LA. Had a much larger fish back then, but this year it was just as tasty.
When it's done (stick a thermometer into the middle and if it's 130°F, it's done), pick off the salt dome, remove the fish, brush off any extra salt and serve.
Contrary to what you might think from being baked under so much salt, the fish doesn't really turn out very salty at all, but it does stay nice and moist and oh so yummy. It's received rave reviews from the family both times we've done it so far.