Combine the pesto sauce, oil, lemon juice and black pepper in a shallow ovenproof dish. Evenly coat the salmon with the pesto marinade. Cover and marinate for at least 2 hours in a refrigerator. To cook the vegetables, place the peppers, onion, garlic and courgettes into a roasting tin. Mix well to ensure that they are coated in oil. Place in a preheated oven 220?C, 425F, gas mark 7 for 20 minutes, turning occasionally. Reduce the oven temperature to 200?C, 400?C, gas mark 6. Place the salmon into the oven and bake uncovered for a further 20 minutes, or until the flesh flakes easily. Place each steak on a small bed of roasted vegetables, and pour any remaining juices over the top. Serve with couscous and freshly chopped basil. NOTES : The Tartan Quality Mark is the hallmark of premium quality Scottish salmon. Each fish has been produced to strict guidelines set down by an independently controlled product certification scheme and has a unique identification number which allows it to be traced back to the farm.