Finely chop the scallion, mince the garlic, and then put them in a shallow dish. Add the grated ginger, soy sauce, Hoisin sauce, oil, lemon juice, and pepper. Whisk sing a fork to combine the ingredients. It is not necessary to add any salt since the soy and oisin sauces are already rather salty.
Put the salmon in the dish and turn it to coat with the marinade. Cover and let stand either 30 min at room temperature or overnight in the refrigerator.
Preheat the oven to 190ºC/375ºF.
Remove the salmon from the marinade, letting the excess marinade drip off, then transfer it to a baking sheet, skin side down. Bake in the middle of the oven about 20 min. alternatively, the salmon may be cooked on an outdoor grill.
Check with a fork to see if the fish is cooked through. Separate and lift the salmon from the skin with a metal spatula and serve (discard skin).