Prepare 4 cups cooked quinoa. Set aside and allow to fully cool to room temperature.
Prepare the tuna marinade by placing all marinade ingredients into a medium bowl and whisking. Add cut up tuna and toss to coat. Refrigerate tuna while preparing the rest of the recipe or up to 20 minutes.
Make the Miso Dressing by adding all dressing ingredients to the bowl of a blender or food processor. Process on high until the mixture is fully blended and creamy. Set aside.
Just before serving, in a large bowl toss 6 cups of mixed greens with 4-6 tablespoons of miso dressing. Compose the bowl by adding 1 cup of cooked quinoa to the bottom of each bowl. Add a mound of dressed mixed greens to the top of the quinoa. Divide the cut up avocado and cucumber to each salad. Place equal portions of the tuna on top of the greens. Place cut up nori strips atop salads and serve immediately.
Serves 4 as a light meal or 6 as a small salad.