Preheat broiler. Brush salmon with 1 tablespoon of the soy sauce. Place on a baking sheet and broil salmon for 10 minutes or until it is cooked through. In a small bowl whisk together, remaining soy sauce, rice wine vinegar, lemon juice, oil, sugar, ginger, and a pinch of salt until sugar is dissolved. Quarter pit and peel avocado and cut crosswise into 1/2-inch slices. Add avocado to dressing and gently turn with a rubber spatula to coat. Plate salmon and divide avocado and dressing between them. Sprinkle sesame seeds over avocado.