Shave the cucumber into long ribbons using a vegetable peeler. Place on kitchen towel to absorb the water then into a bowl with the vinegar and season generously. Leave for 15 minutes.
Place the seasoned salmon skin side down in a hot pan with a little oil. Cook for 5 minutes or until the skin is golden and crisp. Turn the salmon over and cook for another 3 minutes. Now turn the heat off and let the salmon sit in the pan for 10 minutes. The residual heat will cook the salmon through.
If you want to try slightly pink salmon, then skip the last stage and remove from the pan immediately.
Drain the cucumber slightly and onto the serving plate alongside the salmon. Drizzle with the dressing and sprinkle with sesame seeds.
