Prepare the marinade by whisking together the soy sauce, brown sugar, olive oil, garlic, ginger, lemon juice, black pepper, and red pepper flakes in a bowl.
Marinate the salmon by placing the fillets in the mixture for at least 10 minutes (or up to 30 minutes for deeper flavor).
Heat a large skillet over medium heat and add a little olive oil.
Sear the salmon for 3-4 minutes per side, or until golden brown and cooked through.
Thicken the glaze (optional): Remove the salmon, add the cornstarch mixed with water to the pan, and stir until the sauce thickens.
Drizzle the glaze over the salmon and garnish with sesame seeds and green onions.
Serve immediately with rice, vegetables, or noodles.