Herb butter turns grilled tuna into something you'll want to make again
Herb butter grilled tuna is tuna cooked hot and fast over direct heat, then finished with a compound butter made from fresh herbs, garlic, and salt. The butter melts into the warm fish, carrying flavor into the meat while the outside stays firm. You need a hot grill, tuna steaks cut at least an inch thick, and butter you've mixed with herbs ahead of time. The whole thing takes fifteen minutes from fire to plate.
The technique works because tuna's dense muscle holds up to high heat without falling apart. Unlike flaky white fish, tuna stays together and actually improves with a hard sear — you get a crust that tastes like the ocean and the grill at once. The herb butter cools slightly as it hits the hot fish, creating a sauce that clings to the meat instead of running off.
Key Takeaways
- Buy tuna steaks at least one inch thick, ideally from the loin, and use them the same day you bring them home.
- Make herb butter at least an hour ahead by mixing softened butter with fresh herbs, minced garlic, lemon zest, and salt.
- Oil your grill grates well and get them hot enough that a drop of water sizzles on contact before you lay the fish down.
- Tuna cooks through in three to four minutes per side over high heat — overcooking dries it out, so watch the time closely.
- Top the fish with a thick slice of herb butter straight off the grill so it melts into the warm meat.
Choosing and preparing your tuna steaks
Tuna steaks come from the loin, the muscle that runs along the fish's spine. They're cut perpendicular to the spine, so you see the cross-section of muscle with a line of darker meat (the bloodline) running through. Buy steaks that are at least one inch thick — thinner cuts dry out before they cook through. The flesh should be deep red or dark pink, firm to the touch, and smell like clean ocean, not fishy or sour.
Pat the steaks dry with paper towels right before grilling. Moisture on the surface steams instead of searing, and you lose the crust. Don't salt the fish until just before it hits the grill — salt draws moisture out and sits on the surface where it can burn. If your steaks are very thick (over an inch and a half), you can bring them to room temperature for ten minutes so the inside cooks evenly, but this is optional.
Making herb butter that holds its shape
Herb butter is softened butter mixed with herbs, garlic, and salt, then chilled until it's firm enough to slice. Make it at least an hour before you grill, or up to three days ahead and keep it wrapped in the refrigerator. Use unsalted butter so you control the salt level — about four ounces (one stick) makes enough for four tuna steaks with some left over.
Soften the butter at room temperature until it's spreadable but not greasy. Mince fresh herbs finely — parsley, dill, tarragon, and chives all work well, alone or mixed. Add one minced garlic clove, the zest of half a lemon, and a quarter teaspoon of salt per stick of butter. Mix everything together with a fork until the herbs are evenly distributed. Spoon the mixture onto plastic wrap, roll it into a log, and refrigerate. When you're ready to use it, slice off a thick coin for each steak.
Setting up your grill for a proper sear
You need high, direct heat to sear tuna properly. If you're using charcoal, let the coals burn down until they're covered in white ash and you can hold your hand over the grate for only two to three seconds. If you're using gas, turn all burners to high and let the grill heat for at least ten minutes with the lid closed.
Oil your grill grates well — use a folded paper towel dipped in neutral oil (vegetable, canola, or grapeseed) and rub it over the hot grates. This prevents sticking and helps build the crust. Test the heat by holding your hand six inches above the grate; you should feel intense heat that forces your hand away in a few seconds. If the grate isn't hot enough, the fish will stick and steam instead of sear.
Grilling the tuna steaks
Season both sides of the steaks with salt and a pinch of black pepper just before they go on the grill. Lay them on the hottest part of the grate and don't move them — let them sit for three to four minutes. You'll see the edges turn opaque as the heat climbs up into the meat. Flip once and cook the other side for three to four minutes. The fish is done when the outside is firm and dark brown and the center is still slightly translucent (medium-rare) or just barely opaque (medium).
Tuna continues to cook after you take it off the heat, so pull it a shade earlier than you think you need to. If you like it cooked through, give it another minute per side, but know that this dries it out noticeably. The best way to check doneness is to press the thickest part with your finger — it should feel firm but still have a little give, like the muscle of your forearm when your hand is relaxed.
Finishing with herb butter
Transfer the tuna to a warm plate immediately after it comes off the grill. Top each steak with a thick slice of herb butter while the fish is still hot. The butter will melt into the warm meat, carrying the herbs and garlic deep into the flesh. Let it sit for a minute so the butter soaks in, then serve right away. A squeeze of fresh lemon juice over the top brightens everything.
If you have leftover herb butter, it keeps in the refrigerator for up to a week and works on grilled fish of any kind, grilled vegetables, or warm bread. You can also freeze it for up to three months — wrap it tightly in plastic and then foil.
Sides and serving
Herb butter tuna is rich and doesn't need much. Grilled asparagus, a simple green salad with lemon vinaigrette, or crusty bread to soak up the melted butter all work well. If you want something starchy, try grilled potatoes or rice pilaf. The fish itself is the main event, so keep the plate simple and let it shine.
Serve the tuna as soon as it comes off the grill. It's best eaten warm, when the herb butter is still melting and the crust is still crisp. If you're cooking for a group, you can grill the steaks in batches and hold them loosely covered with foil while you finish the rest, but don't let them sit more than a few minutes.
Frequently Asked Questions
Can I make herb butter with dried herbs instead of fresh?
You can, but use about a third of the amount — dried herbs are more concentrated. Dried tarragon and dill work better than dried parsley, which loses most of its flavor. Fresh herbs are worth seeking out for this dish because the butter is the only sauce.
What if I don't have a grill?
Use a cast iron skillet over high heat on the stovetop. Heat the pan until it's smoking, oil it lightly, and sear the tuna steaks for three to four minutes per side. You'll get a good crust and the same result. Finish with herb butter the same way.
How do I know if my tuna is fresh enough to eat?
Buy it from a fishmonger who sells sushi-grade tuna, or ask your grocery store which days they receive fish. The flesh should be bright red or deep pink, firm, and smell clean. If it smells strongly fishy or ammonia-like, don't buy it. Use it the same day you bring it home.
Can I cook tuna steaks ahead and reheat them?
Reheated tuna becomes dry and tough. Cook it fresh and serve it warm. If you need to make it ahead, cook the tuna, let it cool, and serve it at room temperature with the herb butter melted over it — this is actually pleasant and works well for a picnic or lunch.
What thickness of tuna steak is best?
One to one and a half inches is ideal. Thinner steaks cook too fast and dry out before the inside cooks through. Thicker steaks are harder to cook evenly without overcooking the outside. Ask your fishmonger to cut them to order if the ones in the case aren't the right thickness.