I baked some Mahi in the oven last night. Here's how I like to bake it... I bake thick snapper filets like this too.
I rub some olive oil all over my baking dish 1st.
Then I add a whole diced sweet onion, some fresh minced garlic (4 to 6 cloves depending on the size dish), and a good amount of nice sized slices of red bell peppers and poblanos. I used 4 bells and 3 poblanos in this one. My baking dish is large.
Then I either use fresh tomatoes that I cut up into small pieces after I de-seed them... or... I will sometimes use 2 cans of rotel tomatoes that I let drain completely before adding into the dish. I don't want extra liquid in the dish because it cooks down on it's own and there ends up being enough liquid.
Then I squeeze the juice of 2 lemons and 2 limes.... add all of it into the dish. Put some salt and coarse ground pepper in and mix everything up.
Season your fish. Salt and pepper is good enough but I also have a little spicy mixture that I put on top of the fish too. The fish in the pic is cut into slices that are about 9" long and about an inch and a half thick. I lay the pieces across the top of my pepper and onion mixture. Then I spray the top of the fish with a light coating of olive oil.
Cover the dish with aluminum foil and bake at 400° for an hour.
Then take the foil off and broil the dish until the fish is crispy on top. This doesn't take long so keep a close eye on it.
Finished... the fish is still dry on top of the mix... but the mix is now full of liquidy goodness.
We eat it over Mexican rice. Everyone fights for the juice. It's packed with flavor. Two pieces of fish have already been removed in this pic.