Cube the sashimi-grade ahi tuna into uniform 1/2-inch pieces and place them in a glass mixing bowl.
In a small ramekin, whisk together the tamari, toasted sesame oil, rice vinegar, and freshly grated ginger to create the marinade.
Pour the marinade over the tuna cubes, tossing gently to coat, and place in the refrigerator for 10 minutes to allow the flavors to meld.
Steam the cauliflower rice in a pan with a splash of water for 3-5 minutes until tender, then season with sea salt.
Roughly chop the macadamia nuts into small pieces to enhance their crunch and buttery flavor profile.
Dice the cucumber into small rounds and slice the avocado into thin wedges.
Layer the cauliflower rice at the bottom of a serving bowl and top with the chilled marinated tuna.
Arrange the cucumber, shelled edamame, and avocado wedges around the tuna.
Garnish the bowl with chopped macadamia nuts, sliced scallions, and a sprinkle of black sesame seeds.