½ cup diced watermelon, in pieces the same size as the tuna
Combine all ingredients except for salt and watermelon. Taste for seasoning before adding salt. The dish needs a bit of salt, but remember the soy and sesame contribute to the sodium load.
Make sure the marinade completely covers the fish, place in a sealable container, and put in the coldest part of the fridge for a few hours up to a day. Before serving, fold in watermelon. Serve with chips, avocado, pickled ginger and sriracha, or like me, chip-sized slices of watermelon.