Remove the woody end of the fennel, then slice thinly. Heat the oil in a frying pan and, at low temperature, simmer the fennel slices for about 10 minutes until tender.
Meanwhile add the spaghetti to a saucepan of boiling water and cook until al dente. Drain and keep it warm in the pan under the lid. Keep a cupful of the cooking water.
Add the chopped garlic, saffron, lemon zest & juice to the fennel. Season with salt & pepper then turn up the heat and cook for about a minute. Stir in the spaghetti and, if necessary, add a drop of oil and/or the cooking water. Warm through.
Chop the parsley and stir this into the pasta.
Serve with grated Parmesan sprinkled on top if you like.