Pat dry with paper towels (discard the sake) and transfer the fish to a baking sheet lined with parchment paper.
Sprinkle both sides of the fish with the salt.
Let it sit at room temperature for 20 minutes. During this time, preheat the oven to 425ºF (218ºC) with a rack placed in the middle. For a convection oven, reduce the cooking temperature by 25ºF (15ºC).
After 20 minutes, pat dry the excess moisture released from the fish.
Place the fish skin side down on the parchment paper and bake for 15-20 minutes, or until the flesh is golden brown.
Grate the daikon radish (I lovethis grater) and squeeze out most of the liquid.
Serve the grilled mackerel on individual plates with the grated daikon and a lemon wedge on the side. Pour a few drops of soy sauce on the grated daikon and use as a refreshing condiment on the fish. Enjoy!
You can keep the leftovers in an airtight container and store in the refrigerator for 2 days.