1 Rinse clementine in hot water, wipe dry and remove a thin layer of the skin with a peeler.
2 Carefully remove any white pith with a sharp knife.
3 Slice clementine peel into thin strips and dip in boiling water for 30 seconds. Lift out with a slotted spoon and rinse under cold water.
4 Juice grapefruit and lemon. In a bowl, mix 1 tablespoon of the juice with half of the clementine strips. Stir in soy sauce and rice vinegar.
5 Rinse salmon and pat dry. Cut into 1.5 cm (1/2-inch) cubes. Add to the citrus and vinegar mixture. Refrigerate and allow to marinate for 40 minutes.
6 Meanwhile, lightly toast black sesame seeds in a dry frying pan over medium heat. Let cool.
7 With a vegetable peeler, peel radish into thin slices. With a sharp knife, cut into very thin strips.
8 Lightly salt radish strips and let stand 10 minutes. Pat dry with a kitchen towel.
9 In a bowl, mix radish strips with remaining clementine peel, sesame seeds and sesame oil.
10 Cut nori seaweed into thin strips. In a dry pan, lightly toast nori. Let cool.
11 Drain salmon well and pat dry with paper towels.
12 Heat oil in a heavy pan over high heat and cook salmon very briefly. Arrange radish strips in little nests on plates. Top with salmon and garnish with toasted nori.