Cut salmon length wise into two portions - each piece should be less than 2.5 inches thick for easy flipping
Sprinkle salt, garlic powder and black pepper evenly on all sides of the salmon. Rub in seasonings
Turn heat on medium. Heat 9 inch non stick fry pan. Add olive oil
Place salmon skin side down on fry pan. You should hear a satisfying sizzle! Lower heat to low immediately
Pan fry salmon skin side down on low heat till the pink flesh is pale 1/2 up from the bottom. You should see the skin change from light (cooked) to dark (uncooked). This should take approximately 7-10 mins depending on how thick your salmon piece is. In the meantime mix the corn starch slurry if you haven't already
Gently flip and cook the top of the salmon for 1 min. The middle of the salmon should still be a darker pink color and the fat shouldn't be rendering out (i.e. white juices coming out)
Gently flip back skin side down
Add the 2 tbsp butter to the pan. As it melts down and starts to foam, spoon it over the salmon. Spoon for 1 min
Remove salmon and put it on your serving plate. Squeeze a bit of fresh lemon juice using the lemon wedge and sprinkle a pinch of salt. Let rest while you work on the pan sauce
Change heat to medium. On same pan add green onions and fry for 30 secs
Add chicken broth/water, soy sauce and let simmer till gently bubbling
Turn heat to low. Add corn starch slurry, stir until sauce thickens (about 1 min). If sauce is too thick add a bit more liquid
Mix in sesame oil
Pour sauce over salmon. Add salt and pepper to taste. Garnish with green onions
Serve immediately