Rub 1 tablespoon of the olive oil over the salmon and season well. Place on a baking sheet and cook in a preheated oven, 190°C (375°F), Gas Mark 5, for 12–15 minutes or until the fish is cooked through and flakes easily.
Meanwhile, heat the remaining oil in a saucepan, add the onion and garlic and cook for a couple of minutes until softened. Stir in the tomato purée, then add the sweet chilli sauce and tomatoes. Bring to the boil, then reduce the heat and simmer until ready to serve.
Cook the pasta in a large saucepan of salted boiling water according to the pack instructions until al dente. Drain, reserving a little of the cooking water, and return to the pan. Stir through the tomato sauce, adding a little cooking water if needed. Carefully flake the fish, removing any skin and bones, and add to the pasta.
Spoon into serving bowls and serve sprinkled with basil leaves.