Preheat a barbecue grill or chargrill pan to a moderate heat and lightly oil the pan. Combine the coriander, salt, cinnamon, cardamom, pepper and ¼ teaspoon sugar in a small saucepan. Measure out 1¼ teaspoons of the spice mixture and rub into one side of each salmon steak.
Add the mustard seeds, white wine vinegar and the remaining 1½ tablespoons sugar to the spice mixture left in the saucepan, and bring to the boil over a moderate heat. Add the zucchini, capsicum and corn and cook for 6–8 minutes until the vegetables are just tender and most of the liquid has been absorbed.
Meanwhile, place the salmon, spice side down, on the grill or chargrill pan and cook, without turning, for 6–8 minutes, or until just tender and cooked through. Serve the salmon, spice side up, topped with the relish.
• Cardamom is sold as green pods or as black seeds. If you are using the pods, crush the pods slightly and peel off the tough, green outer skin to release the seeds. * • You could serve the salmon with salad greens, steamed vegetables or with steamed or boiled white rice. * • You can use frozen kernels if you prefer; just thaw and drain before use.