01 - Preheat oven to 400°F. Line a baking sheet with parchment paper and set aside.
02 - In a small saucepan, whisk together tamari, maple syrup, rice vinegar, sesame oil, minced garlic, and grated ginger. Place over medium heat and bring to a gentle simmer.
03 - In a separate small bowl, dissolve cornstarch in water to form a smooth slurry. Stir the slurry into the simmering saucepan and cook, stirring continuously, until the sauce thickens and coats the back of a spoon, about 2 to 3 minutes. Remove from heat.
04 - Arrange the salmon fillets on the prepared baking sheet, skin side down. Brush each fillet generously with the thickened teriyaki sauce, reserving a small amount for finishing.
05 - Bake for 12 to 15 minutes, or until the salmon is just cooked through and flakes easily when tested with a fork. Internal temperature should reach 145°F.
06 - Remove the salmon from the oven and brush with any remaining sauce. Sprinkle with sesame seeds and thinly sliced spring onions before serving.