Preheat the oven to 400 degrees F. Line a baking sheet with foil.
In a medium saucepan, whisk together the soy sauce, water, rice vinegar, maple syrup, oil and cornstarch until smooth. Stir in the ginger and garlic.
Set the saucepan over medium-high heat and bring the soy sauce mixture (teriyaki sauce) to a gentle boil, whisking occasionally. Continue to cook (keep whisking occasionally) until the sauce thickens, 5 to 6 minutes. Transfer half of the sauce to a bowl and reserve.
Place the salmon fillets on the prepared baking sheet, skin side down (if the fillets aren’t skinless). Brush each fillet with 1 tablespoon of the teriyaki sauce.
Cook the salmon until it is just cooked through, 6 to 12 minutes, depending on the thickness of the fillets. In the last two minutes of cooking, place the salmon under the broiler to brown the sauce a bit. Take care not to burn it. The salmon fillets should easily release from the skin.
Serve the salmon on top of the cooked cabbage. Garnish with sesame seeds and sliced green onion, if desired.
Heat 1 teaspoon avocado oil in a large nonstick skillet set over medium-high heat. Add the white & light green sections of the green onion, ginger and garlic to the oil. Cook, stirring, for 1 minute.
Add the remaining avocado oil and the sesame oil to the pan. Add the Napa and red cabbage.
Cook the cabbage, stirring constantly, until it is slightly wilted, 2 to 3 minutes. Stir in the reserved teriyaki sauce.
Remove from the heat and stir in the green sections of the green onion.