• All ingredients ready? Let's begin!
  

Ponzu Sauce

• Using a glass jar (a mason jar works well) with a lid, combine the soy sauce, lemon zest, lemon juice, orange juice, mirin, bonito flakes, and kombu.
  
• Place the lid on the jar and shake well to combine.
  
• Refrigerate overnight.
• Strain the sauce through a sieve to remove the bonito and kombu before using it.

Tuna

• In a small mixing bowl, whisk together the ponzu sauce, sesame oil, and soy sauce. Add the grated ginger and scallions to the bowl and stir well to combine. Set this aside.
  
• In a large skillet over medium-high heat, warm the vegetable oil until fairly hot. Add the cold tuna to the pan and sear it on all sides using tongs to turn and hold the tuna. Do this for approximately 30 seconds per side. The outside flesh will turn a gray color while the interior will remain red and uncooked.
  
• Remove the fish to a clean cutting board and allow it to rest for a few minutes until cool enough to handle.
• Using a very sharp chef’s knife or a specialty serrated knife, slice the tuna against the grain into 1/4-inch thick pieces.
  
• On a serving platter, arrange the sliced tuna in a shingle pattern with lemon slices between some of the pieces. Spoon the sauce over the tuna, being generous. Garnish with the sesame seeds.
  
• Place cooked rice in individual serving bowls. Using chopsticks, grab a piece of tataki and eat it over the rice so that the excess sauce drips into the rice. Enjoy the fish and then enjoy the seasoned rice to finish the meal.