This Filipino-style tuna steak in soy sauce delivers big, bold savoury flavour with minimal effort. The tuna is marinated in a sweet-salty soy mixture, simmered until tender, then pan-fried for crispy edges. A weeknight-friendly main course ready in under an hour.
In a small bowl, combine the soy sauce, lemon juice, and sugar. Stir until the sugar is dissolved.
Place the tuna steaks in a saucepan and pour the soy sauce mixture over them.
Add the ground pepper and the minced garlic. Flip the tuna steaks to distribute the pepper and garlic evenly.
Cover and marinate for 30 minutes.
Bring to a boil over medium heat, then reduce to low and simmer for 5 minutes.
Add the water, bring back to a boil, then reduce heat and simmer for another 5 minutes. Carefully remove the tuna steaks from the sauce and set aside. Reserve the sauce.
Heat the vegetable oil in a non-stick skillet over medium-high heat.
Pat the tuna steaks dry with paper towels, then fry for 2–3 minutes per side until golden brown and crispy on the edges. Remove from the pan.
In the same skillet, sauté the onion rings for 30 seconds until slightly softened, then add the fried tuna steaks back to the pan.
Pour the reserved sauce over the fish and onions. Let it boil for 1 minute until the sauce is slightly reduced and glossy. Remove from heat and serve immediately.