slimply grill the tuna with a little olive oil
when done to your likeness, place on steamed brown or jasmine rice
drizzle with lime or lemon juice
splash of soy sauce or fish sauce
opt:
thinly sliced red onion
slivered ginger
chopped roasted garlic
chopped thai chilis
chopped cilantro, basil or mint or all three
i had cobia done like that last night with all the toppings
it was awesome
cheers