Clean and remove watermelon from its rind. Cut into large enough slices to place on the grill. Peel and cut the onion in half.
In a small bowl, mix together the togorashi, chili flakes, and sesame seeds. Then, using your hands, crush the nori (seaweed) sheet into small pieces and add to the togorashi mix.
Whisk together the sesame oil, soy sauce, rice wine vinegar, and ½ of the lemon (juice) to create a liquid marinade.
In a sealable container or zip lock bag liberally season the watermelon with the togorashi mix and half of the liquid marinade. Shake to distribute evenly, let sit 30 minutes. Set aside the remaining marinade.
Heat the grill, then add watermelon. Grill until grill marks appear on each side of the watermelon slices (roughly 5 minutes per side). Grill the onion. Remove from grill and let cool.
Once cool enough to handle, cut the watermelon slices into medium diced cubes, or traditional Poke size. Using a strainer, press out excess water from watermelon. (it will be a lot of water).
Return your watermelon to a resealable container or zip lock bag. Small dice the grilled onion and add it to the watermelon. Add the remaining liquid marinade, minced garlic and sprinkle with the togorashi mix and salt and pepper. Let sit refrigerated.
Clean and cut avocadoes into small dices and place in a bowl. Finely chop cilantro and add to the avocado. Squeeze in the other half of the lemon, and finish with salt and pepper.
When ready to serve, strain off any excess liquid marinade that you don’t want present in the watermelon poke. (There may be a lot of water).
Thinly slice scallions and add to the watermelon poke. Serve Poke with avocado mix. Topped with scallions and togarashi mix. Taste and adjust with salt & pepper if needed.
Try serving with fried Rice Paper (Banh Trang) or fried Rice Noodle.