Preheat the oven to 175 degrees Celsius (350 degrees Fahrenheit)
In a bowl whisk together the olive oil, crushed garlic, basil, capers, lemon juice and salt and pepper. Set aside
Place the chopped red onion, tomatoes, green beans, asparagus, olives and artichoke hearts on a baking sheet. Drizzle 2/3 of the dressing over the vegetables and roast in the oven for 12 minutes.
Place the salmon fillets on the veggies and top with a slice of lemon. Return to the oven and bake for a further 10-12 minutes until the salmon is cooked through.
Pour the remaining dressing over the veggies and salmon and sprinkle with basil before serving.