1. Preheat the oven to 200C, and line a large baking tray with foil and baking parchment. In a large bowl, toss together the red and yellow peppers, onions, courgettes and garlic with the 3 tbsp of the olive oil. Season with salt and black pepper. Place in the oven for 20 minutes, until just beginning to brown.
2. Remove the tray from the oven and stir the vegetables. Add the vine tomatoes and the salmon fillets, brushing with the remaining olive oil. Return to the oven for around 10 minutes until the salmon is just cooked through. Serve scattered with torn basil leaves.