In a large pan, add in oil and turn to medium heat.
Slice half a red onion and yellow onion into thin strips.
Place in a mixing bowl and coat in corn starch.
Once they are equally coated, drop one onion into the oil and see if it fizzles.
If it fizzes, drop in the rest and spread them out so they are not crowded.
Once they are very lightly golden brown, strain off the oil and add to a paper-lined plate to cool.
In a small mixing bowl, add the kewpie, miso, honey, rice wine vinegar, lemon juice, dijon, a pinch of salt and zest.
Whisk until creamy and incorporated.
Add in tuna and mash with a fork until you get flaky, small tuna pieces.
Add in celery and spring onion and mix through.
Crumble a packet of roasted seaweed over top with your hands, not mixing through.
Do the same with the fried onions, not mixing them through, just sitting them on top.
