Coat the tuna with the marinade and place in the refrigerator for 30 minutes. Add 1/2 cup of the olive oil to a medium saute pan and turn on medium-high heat. Julienne all of the vegetables and saute them quickly, 3 to 4 minutes. Set aside and keep warm. When the tuna is ready, take it out of the marinade and coat with the black sesame seeds. Pour another 1/2 cup of olive oil into a medium saute pan. Place on medium-high heat and sear tuna on both sides until golden brown. Let the tuna cool for 5 minutes. In a blender, blend the chives and remaining oil and strain. Place the strained mixture into the refrigerator until needed. To serve, mold the rice in a ramkin and place in center of the plate. Place the vegetables on top. Next, slice the tuna into 1-inch thick slices. Place them around the rice, making sure to overlap them just a bit. Spoon the chive oil around the plate and garnish with scallions.