STEP 1: In a small saucepan over medium heat, combine tamari, water, maple syrup, vinegar, ginger, garlic, 1/4 tsp. pepper and sesame oil. Whisk to combine.
STEP 2: In a small bowl whisk cornstarch and water to combine and add the saucepan.
STEP 3: Whisk for a couple minutes until teriyaki sauce thickens. Turn off heat.
STEP 4: Heat a skillet over medium high heat and add avocado oil until shimmering. Season the yellowtail on both sides with salt and pepper. Place the fish skin side down and cook for 4 minutes.
STEP 5: With a spatula flip the fish and cook another 3-4 minutes and baste the fish with the teriyaki sauce.
STEP 6: Serve over rice and garnish with sesame seeds and sliced scallions.