In a medium bowl, combine the low-sodium soy sauce, 4 tablespoons of water, honey, brown sugar, minced garlic, minced ginger, and lemon juice. Whisk until well combined and the sugar is dissolved.
In a small bowl, mix the cornstarch with the remaining 4 tablespoons of water until smooth. Add this mixture to the teriyaki sauce and whisk again.
Heat a large skillet over medium-high heat. Once hot, add the salmon fillets to the pan, skin-side down (if they had skin). Cook for about 4-5 minutes without moving them, allowing a golden crust to form.
Gently flip the salmon fillets and pour the teriyaki sauce over them. Reduce the heat to medium and let the sauce simmer for about 4-5 minutes, spooning the sauce over the salmon occasionally.
Once the salmon is cooked through and flakes easily with a fork, remove it from the heat. Serve immediately, garnished with chopped green onion and sesame seeds if desired.