Sprinkle salt on the Spanish mackerel fillets and let them sit for 5 minutes. Pat dry with paper towels.

Cut the cabbage into large pieces, halve the cherry tomatoes, and crush the garlic clove.

Heat half of the olive oil in a pan over low heat, add garlic, and sauté until fragrant. Add the mackerel fillets and cook on medium heat for 3 minutes per side until golden. Remove the fish.

Wipe the pan clean, heat the remaining olive oil, and sear the cabbage on both sides over medium heat. Add cherry tomatoes, sake, and water, bring to a boil, cover, and simmer on low heat for 7 minutes.