Place the cooked brown rice in the center of a serving bowl as the base.
Dice the sushi-grade ahi tuna into bite-sized half-inch cubes and place them in a glass mixing bowl.
In a small jar, whisk together the tamari, lime juice, sesame oil, chipotle powder, sea salt, and black pepper until well combined.
Pour half of the dressing over the tuna cubes, tossing gently to coat, and let them marinate for 5 minutes in the refrigerator.
Prepare the vegetables by dicing the cucumber, thinly slicing the radishes, and mincing the jalapeño.
Arrange the marinated tuna, sliced avocado, cucumber, radishes, and jalapeño over the rice in separate sections.
Drizzle the remaining dressing over the entire bowl and garnish with freshly chopped cilantro before serving.