1. Heat the oil in a skillet over medium heat. Add the corn and cook for 2 minutes. Add the sugar, season with salt and pepper and cook for another minute.
2. Transfer the corn to a small bowl and cool slightly. Stir in the tomatoes, onion, cilantro, jalapeño pepper, lime zest and lime juice. Adjust the salt and pepper to suit your taste. (This can be made in advance and stored in the refrigerator for up to 2 days.)
For the salmon:
3. Preheat the grill to medium-high.
4. Drizzle the salmon fillets with olive oil and season with salt and pepper.
5. Grill the salmon on each side until it is just cooked through, about 5 minutes per side.
6. Spoon the relish over the salmon fillets and serve.