Steps

1. Cut off the core of the cabbage (1/4 head, 400g) at an angle.
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2. Separate the cabbage into about three sections, wash the outer leaves with water, and drain them thoroughly.
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3. Lightly crush a few leaves of cabbage at a time and thinly slice them to about 5mm width. If the slices are too long, cut them in half before slicing. (Key Tip!) Slicing slightly thicker than julienne will enhance the cabbage's sweetness and texture, and improve how it coats with the dressing.
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4. Place the cut cabbage in a heatproof bowl, along with the remaining tough core pieces.
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5. Add 2 pinches of salt and 2 pinches of sugar to the cabbage and mix thoroughly until it becomes glossy. (Key Tip!) Salt and sugar not only season but also help wilt the cabbage through osmosis, allowing it to absorb flavors better. If you encounter tough core pieces while mixing, break them into smaller, bite-sized pieces.
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6. Cover with plastic wrap and microwave for 5 minutes at 600W until piping hot. (Key Tip!) Thoroughly heating the cabbage, rather than eating it raw or lightly cooked, brings out its sweetness and dramatically improves how it coats with the dressing.
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7. In a large bowl, combine 3 tbsp of mayonnaise, 2 tbsp of ponzu sauce, and 1 can of tuna (undrained). Mix thoroughly until the mixture becomes thick and creamy. (Key Tip!) Emulsifying the mayonnaise, ponzu, and tuna oil creates a thick dressing that adheres well to ingredients. If it remains watery, the flavor might seem weak.
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8. Transfer the microwaved cabbage to a colander, and carefully remove the plastic wrap, being mindful of steam burns. (Key Tip!) Mixing the piping hot cabbage directly with the dressing can cause the mayonnaise to separate and the flavor to become diluted. Always let it cool slightly in a colander first.
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9. Spread the cabbage on the colander and let it rest for 5 minutes to cool, ensuring air circulation to prevent heat buildup. (Key Tip!) Transferring to a colander allows air to circulate and cool it faster. If you let it cool in a heatproof container, the container's residual heat can make the cabbage soggy.
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10. Once the cabbage is only slightly warm, drain it well and add it to the bowl with the dressing. (Key Tip!) Instead of dumping the cabbage into the sauce all at once, drain it and add it gradually to the dressing.
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11. Toss to coat the cabbage thoroughly with the dressing. (Key Tip!) The finely flaked tuna acts as a great binder, helping the dressing cling to the cabbage. The sauce should be well-absorbed by the cabbage.
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12. Transfer to a serving dish and generously sprinkle with ground sesame seeds. (Key Tip!) Adding ground sesame seeds at the end enhances the overall richness and brings out their nutty aroma.
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13. Optionally, top with plenty of shredded nori seaweed. (Key Tip!) Shredded nori adds both flavor and umami. If the taste feels lacking, adding umami from ingredients like seaweed, sesame seeds, or bonito flakes is a healthier and less risky way to adjust the flavor than adding more salt.
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