1. Melt butter in large frying pan and gently fry onion until soft.
  2. Add pepperoni, mushrooms and capsicum and cook gently for 5 minutes.
  3. Mix in wine, lemon juice, and tomatoes with their juice.
  4. Allow sauce to come to boil, lower heat and simmer for 15 – 20 minutes, or until thickened, stirring occasionally.
  5. Cook and drain spaghetti. Mix in half the sauce and serve with rest of sauce spooned over top. Sprinkle with parmesan cheese.