Shime Saba (Japanese Cured Mackerel)

Fillet the mackerel. Remove the rib bones, don't worry about the pin bones running along the sides. Lay the fillets of a rack and salt generously on both sides. The mackerel will drip water so have something underneath. Leave the fillets to cure for an hour. Once they are done they will be firm to the touch. Gently rinse the salt off under a cold tap and pat dry. Place in a sousvide bag with a few sripts of lemon rinds and enough rice vinegar to cover in the bag, and add the sugar. seal under full vacuum and fridge for 45 mins. Lay the fillets on a chopping boards and gently rub the corner of the shiny side of the skin until it starts to come away. Pinching it, gently pull the skin from the fish and discard. Now you can remove the pin bones if you wants to, or leave them. Finely slice the fillets about a centimeter thick and serve with soy and wasabi.