To marinate the tuna, combine the juice of 1 grapefruit, garlic and fresh ginger. Marinade the tuna in the grapefruit mixture for 1 hour, flipping half way through.
For the coconut rice, bring 2/3 c Jasmine rice, 1 c coconut milk and 1/4 c water to a boil. Reduce to a simmer and cook for 15 minutes.
After 15 minutes, remove from heat and let sit for 10 additional minutes before fluffing with a fork and adding 2 T lime juice.
For the "jiggy" greens, heat sesame oil over medium heat in a saucepan.
Add garlic and red chili and cook until fragrant, about 2 minutes.
Add bok choy and broccoli. Saute until soft, about 5 minutes.
Add 1 T fish sauce, toss and set aside.
To cook the tuna, heat 1/4 c sesame oil over high heat. When oil is hot, but not smoking, sear the tuna for about 2 minutes on each side.
To serve, plate the coconut rice, then the greens, with the tuna on top. Garnish with scallions and cilantro.