In a flat, shallow dish, combine the soy, rice vinegar, sambal, white and light green scallions, garlic and ginger. Add the tuna and roll around to get the marinade on all sides. Cover and let sit in the fridge for up to 2 hours, turning the tuna periodically.
Remove the tuna from the fridge and let sit in the marinade outside of the fridge for 20 to 30 minutes.
When the tuna has come to room temperature, remove it from the marinade. With a paper towel, gently remove some of the excess marinade.
Coat a large saute pan with peanut oil and bring it to a VERY high heat. When the pan is VERY hot but not quite smoking, pull the pan off the heat and add the tuna to the pan. Return the pan to the heat and sear the tuna for 1 minute on each side.
Remove the tuna from the pan, let rest for 4 to 5 minutes and slice into 1/4 to 1/2-inch thick slices. Sprinkle with the dark green sliced scallion tops.
Serve immediately with a little extra soy on the side if desired.