Fill a large pot of water about a 1/4th of the way, then bring to a boil.
Add cauliflower florets and chunks to a food processor and pulse blend until it resembles grains of rice. Note: do not just blend as the cauliflower will be too fine. Add the cauliflower to a mesh strainer, then set it over the pot of boiling water (it should not be touching the water). Cover with a lid then allow it to steam for 10 – 15 minutes. Once it finishes, set aside to cool, ideally in the fridge.
Mix together the ingredients for the sauce. Set aside.
Use a knife to thinly and finely dice, almost mince, the tuna, then add to a bowl along with the green onions and the sauce. Fold everything together.
Once the cauliflower has completely cooled and is maybe chilled, bring everything together. Evenly divide the rice among 4 portions, then top with poke. Add about 2 teaspoons of sesame seeds to each one then add your favorite toppings.
Enjoy!