In a small saucepan, whisk together the miso, mirin, sake, and sugar. Bring to a simmer and remove from the heat.
Coat the salmon in the miso sauce and marinate for 1-2 hours.
Preheat the oven to 400°F.
Place the rice, 4 cups of water and a pinch of salt in a large saucepan. Bring to a simmer, reduce heat to low, cover, and cook for 20 minutes, until the grains are tender.
Place the bok choy and the salmon on baking sheets, discarding any remaining marinade. Toss the bok choy with oil and a pinch of salt. Roast both the salmon and bok choy for 12-15 minutes, until cooked through.
To make the lomi-lomi tomatoes, combine all ingredients in a mixing bowl until well-coated.
To serve, divide the rice, salmon, and bok choy between plates, top with lomi-lomi tomatoes and furikake and serve with lemon wedges.