In a resealable plastic bag, combine the soy sauce, garlic, lemon juice, and sugar well. Add the salmon, coating it well, and let it marinate, sealed and chilled, for 30 minutes.
Remove the salmon from the bag, discarding the marinade, pat it dry, and press 2 teaspoons of the black pepper onto the skin side of each piece of salmon, coating it thoroughly. In a heavy skillet heat the olive oil over moderately high heat until it is hot but not smoking and in it saute the salmon for 2 to 3 minutes on each side, or until it just flakes.
Transfer the salmon with a slotted spatula to paper towels and let it drain for 30 seconds. Serve with Cucumber Vinaigrette.
Puree cucumber with vinegar in a blender until very smooth. Add sesame oil and blend until emulsified. Season with salt and pepper.
Yield: 1 1/2 cups