Add all of the ingredients (except the tuna steaks) to a large bowl or baking dish – large enough to fit the tuna steaks in. Whisk well.
Add the tuna steaks. I used a flat tray just so the tuna steaks were well coated with marinade and could sit in one layer.
Marinate for 30 minutes in the fridge.
Cook
Preheat a large frying pan or griddle pan to medium-high heat and brush it with a little oil.
Remove the tuna steaks from the marinade, shaking well to get rid of any excess.
Add the tuna steaks to the pan and cook on each side for about 3 minutes. This will get you a medium-rare grilled tuna steak. If you prefer your tuna well done, cook on medium heat for 5 minutes on either side until you reach your desired doneness.
Rest, slice and serve
Remove the grilled tuna steak from the pan and allow to rest on a plate for a few minutes. This allows the flavors to fully meld and for the tuna to finish cooking completely. You can cover with foil to keep them warm.
(Optional step) While the tuna steaks are resting, pour the marinating liquid into a small saucepan and heat over low heat. Add 1/4-1/2 cup of water if needed to make more sauce. Allow to simmer for about 5 minutes until it has slightly thickened. You serve the tuna with this sauce.
Slice the grilled tuna steaks horizontally into strips – this will reveal how they’ve been cooked and if they need a little more cooking time. Drizzle with the simmered marinade sauce, if using, and sprinkle with fresh cilantro before serving.
Video
Notes
Use Fresh Tuna: I recommend going to a fish market or fish counter to get the best, freshest tuna. Not only does it taste better, but fresh, high-quality tuna will have a better texture too.
Marinate for Flavor: Just like steak and chicken, tuna steak soaks up flavors from marinades – and it’ll help elevate the natural taste of the fish. Just an extra 30 minutes in the fridge can make a world of difference to the flavor.
Preheat and Oil Your Grill: The steaks need to be seared – so let your pan or grill preheat to the right temperature before adding your fish. A little oil will stop it from sticking to the pan – and help to cook the outside quickly.
Grill Quickly: A high heat and a quick cooking time will make this recipe a success. The high heat sears the outside of the steak, sealing in its juiciness and flavor and preventing overcooking.