In a small bowl, whisk up all of the ingredients from soy sauce to lime juice, and set aside.
Place the cubed ahi in a medium sized bowl, and add the onions, scallions, cilantro, and avocado.
Pour the sauce over the top of the mixture, and blend gently and briefly, making sure you don't break up the avocado too much.
Cover, and place in the fridge to chill for about an hour.
Serve with sides like Serrano Red Cabbage Slaw from this site, coconut black rice, seaweed salad, tortilla chips, plantain chips, and seaweed snack sheets. And garnish with minced red onion, minced red cabbage, chopped cilantro, Maldon Salt Flakes, and chili sambal. Or, however you like it!