Snap off the woody ends of the asparagus. Cut each stalk crosswise diagonally into 2.5 cm pieces.
Heat cooking spray in a nonstick frying pan over a medium-high heat. Add garlic and chilli flakes and sauté 30 seconds. Add the salmon and cook 3 minutes each side.
Cook the pasta in lightly salted boiling water according to pack instructions, adding the asparagus 3 minutes before the end. Drain well, return to the pan, add lemon juice and soft cheese, and stir over a low heat for 1 minute.
Break the salmon into bite-sized chunks, removing any skin and bones. Add to the pasta, toss gently and serve sprinkled with black pepper and dill.