The Recipe

Swordfish's firm, meaty texture holds up to bold flavors without falling apart. Cilantro pesto butter does two things at once: it cooks into the fish as it sears, and it melts over the top as you plate, so you get the herb flavor both baked in and fresh. The butter keeps the flesh moist while the high heat creates a golden crust.

This is a weeknight dinner that looks like you spent an hour in the kitchen. Start to finish, it takes about 20 minutes.

Key Takeaways

  • Pat the swordfish completely dry before searing so the surface browns instead of steaming.
  • Make the cilantro pesto butter ahead and freeze it in a log, then slice rounds onto the hot fish as it rests.
  • Swordfish steaks need high heat and a short cooking time — about three minutes per side for a one-inch steak.
  • The butter will brown and smell nutty; that's the signal to plate immediately while the fish is still hot.

Ingredients and Proportions

For two swordfish steaks (about 6 ounces each, one inch thick), you will need one stick of softened butter, one cup of packed cilantro leaves, two cloves of garlic, the zest and juice of one lime, salt, and pepper. The cilantro should be fresh and dry — wet leaves will make the butter break when you blend it.

If you cannot find fresh cilantro, flat-leaf parsley works, though the flavor will be milder and more herbaceous. Mint is another option if you want something brighter and cooler. The principle stays the same: soft herbs, fat, acid, and salt.

Making the Cilantro Pesto Butter

Pulse the cilantro, garlic, lime zest, and a pinch of salt in a food processor until the herbs are finely chopped but not yet a paste. Add the softened butter and pulse again until the mixture is even and the herbs are distributed throughout. Taste and adjust salt — the butter should taste slightly salty because it will melt over unseasoned fish.

Lay a piece of plastic wrap on the counter and spoon the butter onto it in a rough log shape. Roll the plastic around the butter and twist the ends tight, like a candy wrapper. Refrigerate for at least an hour, or freeze for up to two weeks. You can make this the day before you cook.

If you are cooking right away and the butter is too soft to slice, chill it in the freezer for 15 minutes while you prepare the fish and heat the pan.

Preparing and Searing the Swordfish

Remove the swordfish from the refrigerator 10 minutes before cooking so it is not cold when it hits the pan. Pat it completely dry with paper towels — this is the single most important step. Moisture on the surface prevents browning and makes the fish stick to the pan.

Season both sides generously with salt and pepper. Heat a cast-iron or stainless steel skillet over medium-high heat until a drop of water sizzles and evaporates immediately. Add a thin film of neutral oil (not olive oil — it will smoke). When the oil shimmers, lay the swordfish steaks in the pan without moving them. Let them sit for three minutes.

Flip once and cook for another three minutes on the second side. The fish should have a golden-brown crust and feel firm but not hard when you press it gently. Swordfish continues to cook as it rests, so pull it from the heat when it is still slightly underdone in the very center.

Finishing with Butter and Serving

Transfer the swordfish to a warm plate and let it rest for two minutes. Unwrap the cilantro pesto butter and slice it into thin rounds — a hot knife helps. Lay two or three rounds on top of each steak while it is still hot. The butter will melt into the fish and pool around it on the plate.

Serve immediately with lime wedges and something to soak up the butter — crusty bread, rice, or roasted potatoes all work. A simple green salad dressed with lemon cuts through the richness and balances the plate.

Why This Technique Works for Swordfish

Swordfish has a high fat content compared to other white fish, which means it can handle a hot pan and a bold sauce without drying out. The flesh is dense enough that it will not flake apart when you flip it, and it will not overcook in the three minutes it takes to develop a crust. The cilantro butter adds moisture and flavor at the moment the fish is hottest, so the herbs stay bright instead of cooking down to nothing.

If you catch your own swordfish, this method works equally well for steaks cut from the loin or the belly. Belly cuts are fattier and more forgiving; loin cuts are leaner and benefit even more from the butter. Either way, the technique is the same.

Variations and Substitutions

You can swap the cilantro pesto butter for other herb butters: tarragon with shallots and white wine vinegar, basil with garlic and lemon, or dill with capers and anchovy. The ratio stays the same — one stick of butter to roughly one cup of herbs, plus salt and acid to balance.

If you prefer not to make compound butter, you can finish the fish with a squeeze of fresh lime juice and a sprinkle of chopped cilantro instead. It will not be as rich, but it will be fresher and lighter. You can also make a quick cilantro oil by blending cilantro with neutral oil and a pinch of salt, then drizzling it over the fish after it rests.

Frequently Asked Questions

Can I make this with frozen swordfish?

Yes, but thaw it completely in the refrigerator overnight and pat it very dry before cooking. Frozen fish often releases more water as it thaws, so extra drying time matters. The cooking time and temperature stay the same.

What if my butter breaks when I blend it?

This usually happens if the butter was too warm or the herbs were wet. Start over with cold butter and completely dry cilantro. If you are in a hurry, chop the cilantro finely by hand and fold it into softened butter with a spatula instead of using a food processor.

How do I know when the swordfish is done?

The flesh should be opaque throughout but still moist in the center. Press it gently with your finger — it should feel firm but yield slightly. If you have a meat thermometer, swordfish is done at 137 to 140 degrees Fahrenheit. It will continue cooking as it rests, so pull it from the heat a degree or two before you think it is ready.

Can I cook this on the grill instead of the stovetop?

Yes. Oil the grill grates well and heat them until they are very hot. Sear the swordfish for three minutes per side over direct heat, then move it to a cooler part of the grill if it is browning too fast. The butter will melt the same way, and you will get a smoky char on top of the herb flavor.

What should I serve with this?

Anything that does not compete with the cilantro and lime: roasted asparagus, steamed rice, crusty bread, or a simple salad of arugula and lemon. Avoid heavy sauces or other strong herbs. A cold white wine — Sauvignon Blanc or Albariño — pairs well with the brightness of the cilantro.