If using a salmon fillet, cut crosswise into 4 equal pieces. Mix together marinade ingredients in a bowl or shallow dish, add the salmon, cover, refrigerate and marinate for 20 minutes.

Heat the oil in a frying pan. Remove the salmon from the marinade, shaking off excess liquid and reserving leftover marinade. Place skin side down in hot oil. Move fish around constantly to keep from sticking. When browned on one side, turn the salmon, reduce the heat and cook, covered, for 6 to 8 minutes. Remove the salmon from the pan, and drain on paper towels. Pour reserved marinade into pan, add the mirin and sugar, and bring to a boil. Add salmon again. Cook until marinade is almost cooked away. Remove salmon from pan, sprinkle with powdered sansho. Slice diagonally and garnish with green peppers Sauteed in the pan, and lemon slices.