For the pickled green coriander, combine vinegar, water, kosher salt, and sugar in a small pot over medium-high heat and bring to a simmer. Stir until sugar and salt are dissolved, then remove from heat and allow to cool slightly. Place coriander into a sterilized glass jar and pour brine over seeds. Allow to cool completely and refrigerate for up to 1 week.
In a small bowl, whisk to combine all ingredients for the marinade.
In a large bowl, combine ahi tuna, macadamia nuts, pickled coriander and benne seeds. Add marinade, toss and refrigerate for 30 minutes to 1 hour prior to serving.
To plate for appetizers, divide poke between serving plates and garnish with pansy flowers, coriander blossoms, nasturtium, purslane, and additional benne seeds. For dinner service, plate with sushi rice.