Step 1 : Combine mirin and sake in a small saucepan and bring to a boil, allowing alcohol to burn off. Turn the heat to low and add red miso paste and sugar, whisking to combine.
Step 2 : Meanwhile, in a small bowl, combine green onions, ginger, oil, tamari, vinegar, 1/16 teaspoon salt and 1/32 teaspoon pepper. Set aside (or place in the refrigerator until serving).
Step 3 :Meanwhile, season the flesh side of the salmon evenly salt and pepper. Preheat an oven-proof skillet over high heat. Once your skillet is pre-heated, add 1 teaspoon oil, quickly swirling to coat, and then immediately add the salmon, flesh side down.