On a large plate, combine equal parts of white and black sesame seeds. Roll the sushi-grade ahi tuna in the seed mixture, fully coating it on all sides.

Heat a medium skillet over medium-high heat and add 1 tablespoon of toasted sesame oil. Carefully place the sesame-coated ahi tuna in the pan and sear for about 15-20 seconds on each side.

Once seared, remove the ahi tuna from the skillet and let it rest for 5 minutes. Then thinly slice the fish into ¼-inch pieces.

In a small bowl, combine 2 tablespoons of shoyu, a pinch of chili flakes, 1 tablespoon of rice vinegar, and freshly ground black pepper. Stir until well blended.

Arrange the sliced tuna on a platter, serve alongside the dipping sauce, and garnish with thinly sliced scallions.