Mix all ingredients of vinegar miso.
Mix all ingredients of ceviche dressing.
Combine vinegar miso, ceviche dressing, and grape seed oil.
Sprinkle tuna belly with salt and pepper and sear the surface with a kitchen torch. Cut into 1⁄2-in. (1-cm) thick slices.
Arrange the mesclun greens, daikon slices, and tuna slices on a plate.
Spoon the vinegar-miso-ceviche dressing over the tuna slices.