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, then lower heat and simmer for 15-20 minutes, or until thickened, stirring occasionally.
  5. Cook and drain pasta with rest of sauce spooned over top.
  6. Sprinkle with parmesan cheese.