1. Add in marinate sauce ingredients and bring it to boil. When it starts bubble, turn down heat to medium low and boil for 5 minutes, then turn off the heat. add bonito flakes in and rest for 5 more minutes. Strain the mixture using a sieve. Cool down the liquid in fridge.
2. Slice salmon into 0.3-5inch think. Place them in a Tupperware with lemon, onion, pepper. Pour cooled soy sauce mixture over it. Marinate for 12 hours. (you can store them up to 2 days)
3. Get a bowl of cooked rice, top with marinated salmon sashimi! Get a big spoon of rice and salmon :)