In a medium-size glass or ceramic bowl, mix together the tamari, sesame oil, ginger and jalapeño. Set aside until ready to serve.
The tamari mixture can sit at room temperature for up to an hour, or covered in the refrigerator for up to six hours.
When ready to serve, add the diced avocado and tuna. Mix gently to combine.
Sprinkle with sesame seeds. Serve immediately.
