Put a pan of water on to boil and cook the spaghetti according to packet instructions. Steam the asparagus in a colander over the pasta for a few minutes until cooked, then remove and cut into bite-sized pieces.
In a frying pan, heat the oil over a medium heat then add the garlic and chilli and cook for a minute, then add the kale and saute for a few minutes until cooked through. If using frozen kale, ensure it is all thawed.
Add the cooked spaghetti to a serving dish with the kale and asparagus, drizzle with the lemon juice, olive oil and lemon zest and toss all ingredients together and season.