- Put the pasta in a large saucepan of boiling, salted water. Simmer for 8 minutes. Drain and return to the pan.
- Meanwhile, heat the oil in a large frying pan, or wok, and fry the onion for 8–10 minutes on a medium heat, until it browns and is caramelised. Remove from the pan.
- Add the mushrooms and fry until they begin to brown.
- Add the lemon zest and cashews. Fry for 1 minute.
- Add the pasta, spinach and onion to the pan.
- Season with salt and pepper.