Prep the base. If using cauliflower rice, warm a skillet over medium heat with oil.
Add cauliflower rice, a pinch of salt, and pepper. Sauté 3–5 minutes until just tender. Add garlic in the last minute if using.
Remove from heat and let it steam off excess moisture. For a salad base, simply toss your lettuce or cabbage and set aside.
Make the spicy sauce. In a small bowl, mix mayonnaise, sriracha, sesame oil, rice vinegar or lime, and soy sauce/tamari. Taste and adjust: more sriracha for heat, more vinegar/lime for brightness, or a bit more mayo for creaminess.
Prep the tuna. If using canned tuna, drain well and flake with a fork.
If using cooked or seared tuna, dice into bite-size pieces. Toss tuna with 1–2 tablespoons of the spicy sauce to lightly coat.
Chop the toppings. Dice cucumber and avocado. Slice green onion.
If using, shred carrots and chop herbs. Keep ingredients in small, neat piles for easy assembly.
Assemble the bowl. Add your base to a bowl. Top with sauced tuna in the center.
Arrange cucumber, avocado, carrots (if using), and green onion around it. Sprinkle sesame seeds and herbs over the top.
Finish and serve. Drizzle with extra spicy sauce as desired. Add a squeeze of fresh lime, a shake of furikake or torn nori, and a few drops of chili oil if you like it extra spicy.
Serve immediately.