In a mixing bowl, whisk together olive oil, soy sauce, lemon juice, minced garlic, grated ginger, black pepper, and sea salt until well combined.
Place the tuna steaks in a shallow dish and pour the marinade over them, ensuring they are well coated. Let marinate for at least 15 minutes (if time allows, marinate for up to 1 hour in the refrigerator).
Preheat your grill or grill pan over medium-high heat.
Remove the tuna steaks from the marinade and discard the remaining marinade.
Place the tuna steaks on the grill and cook for about 2-3 minutes on each side for medium-rare (adjust cooking time for your preferred doneness).
Once cooked, remove the tuna steaks from the grill and let them rest for a couple of minutes.
Serve the grilled tuna steaks on a plate, optionally garnished with fresh herbs.