Make the dressing: Combine all of the ingredients for the wafu dressing in a mixing bowl until everything is thoroughly incorporated.
Cook the dressing (optional): If you want to remove some of the pungency of the onion and bring out its natural sweetness you will need to cook the dressing. Do this by placing the mixed dressing in a small pot. Place this over medium-high heat and let the dressing come to a boil. Stir the dressing for 30 seconds then take the pot off the heat.
Let it cool down: Let the dressing cool down for about 15 minutes in the pot before transferring it to a jar. Place this jar in your fridge and let it completely cool before using.
Assemble a salad in a bowl, pour the wafu dressing over top and enjoy!