Cook spaghetti according to packet directions until al dente. Drain and place spaghetti in a greased 1.5 litre casserole dish.
Melt butter in medium saucepan over low heat. Remove from heat and stir in sour cream, lemon peel and lemon juice. Mix until smooth. Pour mixture over spaghetti in casserole dish. Mix well.
Bake 15 to 20 minutes in the preheated oven or until heated through. Remove from oven and add grated Parmesan cheese and parsley. Season with salt and freshly ground pepper to taste. Serve immediately.