Most chefs will tell you that if you have a pristine piece of fish, you don’t need to do a lot to it. A little oil, a little salt, a squeeze of lemon and a brief stint on the heat are all it needs to blossom and shine.
Most of the time, I agree. Truly fresh fish — either pulled straight from the water or properly frozen moments after being caught — doesn’t need much by way of adornment. As long as you don’t overcook it, your dinner will be divine.
That said, there are few things that aren’t improved by a drizzle of melted butter — fish fillets included.
Melted butter serves as the base for several classic sauces for fish, including amandine and meunière, with good reason. It’s a rich, silky contrast for the lean fish, and these kinds of sauces are a boon for the home cook: Melting some butter, then jazzing it up with nuts or aromatics is about as easy as pan sauces get. Yes, they might be slightly more work than that squeeze of lemon, but not much more, and you get a lot back for your effort.
The most time-consuming part of this recipe is pitting and slicing the olives. But if you’re feeling very lazy or overwhelmed, you can buy pitted olives, and even skip the slicing; just quickly chop or tear them up into coarse pieces. The slices may be a neater presentation, but there’s a rustic charm to a ragged mess of olive bits. Once you swirl them in all that garlicky butter, they will taste the same. Use your favorite olives here. I like a mix of black and green because it’s pretty, but using all good-quality Kalamata or Castelvetrano does good things, too.
As for the fish, always use the freshest and preferably most sustainable fillets you can find. What’s most important here is thickness: Look for pieces that are all about an inch thick so they cook evenly, but not too quickly, giving the olives and garlic a chance to mellow in the oven. If you can find only thinner fillets, cook the olive butter for an extra minute or two on the stovetop, then take a few minutes off the cooking time once you add the fish. This will keep it from overcooking, which even a bath of melted butter cannot fix.
