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Kobujime Tuna Tataki with Morita-Yuzu Ponzu over Cold Soba

Kobujime Tuna Tataki with Morita-Yuzu Ponzu over Cold Soba

Listen, if you are eating raw tuna without curing it first, you are leaving half its potential flavor on the cutting board. We are using a classic Japanese kobujime (kombu cure) to pump the fish full of natural glutamates before flash-searing it tataki-style. Paired with a smoky Mexican morita chile ponzu and cold green tea soba noodles, this is the dinner I make when I want something intensely savory but totally refreshing.

Kenji Nakamura
Kenji Nakamura
Prep: 50 minutes
Cook: 15 minutes
2
medium
dinner
rawfermentationumamifusion+1

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Timeline

1 hour 4 minutes
0m15m30m45m1h
Cure Tuna
45m
Make Morita Ponzu
Boil Water
10m
Cook Soba
Chill Soba
Prep Tuna Crust
Heat Skillet
Sear Tuna
Slice Tataki
Plate and Serve

Ingredients

  • 1 lb sushi-grade tuna saku block(Look for a uniform rectangular block for even searing)
  • 2 sheets dried kombu(Large enough to wrap the tuna block)
  • 2 tbsp sake(For softening the kombu)
  • 1 dried morita chile(Stemmed and seeded)
  • 1/4 cup soy sauce(High quality Japanese soy sauce)
  • 2 tbsp mirin
  • 2 tbsp yuzu juice(Can substitute equal parts lime and mandarin juice)
  • 8 oz dried green tea soba noodles(Also called cha soba)
  • 1 tbsp toasted sesame oil
  • 1 tbsp shichimi togarashi(Japanese 7-spice blend)
  • 1 tsp ground cumin
  • 1 tbsp grapeseed oil(Or any neutral high-heat oil)
  • 2 scallions(Thinly sliced on the bias)

Instructions

  1. 1

    Wipe 2 sheets dried kombu with 2 tbsp sake using a paper towel to slightly soften them and activate the surface glutamates. Tightly wrap the 1 lb sushi-grade tuna saku block in the softened kombu, wrap securely in plastic wrap, and refrigerate to cure.

    45 min

    Tip: Do not wash the kombu with water; the white powder on the surface is pure umami.

  2. 2

    While the tuna cures, lightly toast the 1 dried morita chile in a dry skillet over medium heat until fragrant, about 30 seconds. Transfer to a mortar and pestle, crush roughly, then whisk together in a small bowl with 1/4 cup soy sauce, 2 tbsp mirin, and 2 tbsp yuzu juice. Set aside to infuse.

    5 min

    Tip: The longer this ponzu sits, the more the smoky, raisiny flavor of the morita will permeate the sauce.

  3. 3

    Bring a large pot of unsalted water to a rolling boil for the noodles.

    10 min

    Tip: Never salt the water for Japanese noodles; they are already salted in the dough.

  4. 4

    Drop the 8 oz dried green tea soba noodles into the boiling water and cook according to package directions, usually about 4 to 5 minutes.

    5 min

    Tip: Stir immediately to prevent sticking.

  5. 5

    Drain the soba immediately and plunge into an ice water bath. Vigorously wash the noodles by rubbing them together with your hands in the cold water to remove excess surface starch, then drain thoroughly. Toss with 1 tbsp toasted sesame oil and refrigerate.

    5 min

    Tip: Washing the noodles is non-negotiable for the perfect chewy texture.

  6. 6

    Remove the tuna from the fridge, discard the plastic and kombu, and pat the fish completely dry. On a plate, mix the 1 tbsp shichimi togarashi and 1 tsp ground cumin, then firmly press the tuna block into the spices to coat all sides evenly.

    5 min

    Tip: The kombu will have drawn out moisture; patting it dry ensures a perfect crust.

  7. 7

    Place a cast-iron skillet over high heat until dangerously hot and smoking. Add the 1 tbsp grapeseed oil.

    5 min

    Tip: Open your windows and turn on your vent hood. You want maximum heat.

  8. 8

    Flash-sear the spice-rubbed tuna in the screaming hot skillet for exactly 30 seconds per side. Remove immediately and transfer to a cutting board.

    2 min

    Tip: Do not let it cook any longer; we want a violent crust and an icy, untouched center.

  9. 9

    Using your sharpest knife, slice the seared tuna tataki into 1/4-inch thick pieces.

    3 min

    Tip: Cut in a single long drawing motion to prevent tearing the delicate flesh.

  10. 10

    Divide the chilled soba noodles between bowls. Top with the sliced tuna tataki, generously drizzle the infused morita ponzu over everything, and garnish with the 2 scallions.

    5 min

    Tip: Spoon some of those crushed morita bits right onto the fish for extra texture.

Chef's Notes

Why this works: Kombu is basically nature's MSG wrap. By curing the tuna in it, osmotic pressure draws out watery liquid and replaces it with pure umami. The morita chile in the ponzu brings a raisiny, smoky heat that bridges the gap between the charred crust of the tataki and the oceanic depth of the fish.

Frequently Asked Questions

How long does Kobujime Tuna Tataki with Morita-Yuzu Ponzu over Cold Soba take to make?

Kobujime Tuna Tataki with Morita-Yuzu Ponzu over Cold Soba takes about 1 hour 5 minutes total. That includes 50 minutes of prep and 15 minutes of cooking.

How many servings does this recipe make?

This recipe makes 2 servings.

What skill level is needed for Kobujime Tuna Tataki with Morita-Yuzu Ponzu over Cold Soba?

This recipe is rated medium — it's intermediate, requiring some cooking experience.

What ingredients do I need for Kobujime Tuna Tataki with Morita-Yuzu Ponzu over Cold Soba?

The main ingredients are: sushi-grade tuna saku block, dried kombu, sake, dried morita chile, soy sauce, mirin, yuzu juice, dried green tea soba noodles, toasted sesame oil, shichimi togarashi, ground cumin, grapeseed oil, scallions.

What type of meal is Kobujime Tuna Tataki with Morita-Yuzu Ponzu over Cold Soba?

Kobujime Tuna Tataki with Morita-Yuzu Ponzu over Cold Soba is categorized as: dinner.