Remove salmon from refrigerator and let rest at room temperature for 10 minutes. Meanwhile prepare sweet and sour sauce.

For the sauce, in a small bowl whisk together cornstarch and soy sauce. Add in pineapple juice, honey, brown sugar, rice vinegar, ketchup and red pepper flakes. Heat 1 1/2 tsp of the oil in small saucepan over medium heat. Add ginger and garlic and saute until lightly golden brown, about 30 seconds - 1 minute. Whisk pineapple juice mixture once more then pour into saucepan. Bring mixture to a boil stirring constantly. Allow to boil, stirring constantly until thickened, 1 minute. Remove from heat

Dab both sides of salmon dry with paper towels, season both sides with salt (use about a heaping 1/2 tsp total). Heat remaining 2 tsp oil in a (heavy) 12-inch non-stick skillet over medium-high heat.

Once oil is shimmering add salmon and cook about 4 minutes on the first side until golden brown on bottom then flip and cook salmon on opposite side until salmon has cooked through, about 2 - 3 minutes longer. Plate salmon, spoon sweet and sour sauce over salmon, sprinkle with green onions or cilantro and sprinkle with sesame seeds.