First make the rice: In a medium saucepot, bring the rice and water to a boil.
Season with a pinch of salt.
Cover, reduce the heat to a simmer, and cook for 30 minutes.
Take off the heat, let the rice sit for 10 minutes, and then fluff with a fork.
In a small bowl, combine the vinegar, sugar, and salt.
Pour the vinegar mixture over the brown rice and toss to combine.
Set aside until ready to use.
Meanwhile, make the tuna: In a large bowl, whisk together the soy sauce, vinegar, sugar, lime juice, sesame oil, ginger, sambal, and scallions.
Add the tuna and toss to coat.
Refrigerate to marinade at least 20 minutes and up to 1 hour.
Spoon the rice equally into four bowls.
Add the tuna and garnish with the cucumber, edamame, carrots, radishes, and sesame seeds.
Serve immediately.
Notes & Wine Advice
Use only sashimi-grade tuna, and make sure it is fresh, not frozen. Freezing will compromise the texture of the fish. When purchasing the tuna, look for pieces without white streaks going through them. The white is connective tissue and is chewy and not desirable.