Dressing:
1. For the dressing, grate the lime and lemon zest into a bowl, squeeze the lemon and lime juice into the bowl, chop the spring onion finely and add to the bowl.
Roll the chili between your hands to loosen the seeds. Cut off the top and slice the chili in half length-wise, scrape out and discard the seeds. Slice length-wise into fine strips, chop finely and add to the bowl. Add the sesame oil, olive oil, fish sauce and soy sauce and mix thoroughly. Add chopped coriander to the bowl as well. Whisk all the ingredients together, season with salt, pepper and sugar to taste.
2. Place the salmon fillet in the freezer for 10 minutes. Slice the salmon thinly and arrange on serving plates, overlapping the slices very slightly. Spoon over the dressing and leave to marinade for 5-10 minutes before serving.
3. Garnish with mixed salad leaves if you like.