In a small bowl, whisk together soy sauce, ginger, miso, garlic, onion powder, sesame oil, red pepper flakes, vegetable broth (or water). Set aside.
Pat salmon filets dry using a paper towel. Salt and pepper both sides. Heat oil in large skillet over medium-high heat. Place salmon filets in hot skillet, skin side down. Cook for 5-6 minutes, pressing flat with a spatula. Flip filets and cook for an additional 1-2 minutes; pour in the sauce and "swoosh" around in the pan.
Cook salmon for an additional 2-3 minutes until cooked through. Remove salmon from skillet and set aside, topping with any remaining sauce. Garnish with green onions and sesame seeds as desired. Serve with rice.
Notes
You can easily make 2 salmon filets and either halve the sauce or just have a little extra goodness :) Thin out the sauce with additional broth/water if you find it too intense.