First, cut the tuna into small, 1/2-1 inch squares and transfer to a bowl.
Next, roughly chop the mango, cucumber, and avocado into small squares and add that to the bowl with the tuna.
In another small bowl, whisk together the soy sauce (or coconut aminos), rice wine vinegar, siracha, sesame oil, and ginger.
Pour the sauce onto the tuna mixture, and add the sesame seeds.
Use a spoon to mix everything together well, ensuring the tuna is coated well.
Do a taste test to determine if any additional seasoning is needed!
Serve immediately, either over a bed of greens, rice, or cauliflower rice, and enjoy!