Rub the tuna steaks with 1 teaspoon of oil, and sprinkle with salt and pepper.
Place the sesame seeds on a medium plate. Dip entire surface of the steak into sesame seeds, pressing to adhere.
Heat a skillet on high heat. When very hot, place the tuna steaks on the hot skillet and cook for 1 to 2 minutes on each side, depending on the thickness. Set aside on a plate.
Meanwhile, prepare salad and soy vinaigrette.
Slice tuna steaks into 16 slices and place on top of arugula.
Drizzle vinaigrette over the top.