In a large saucepan, heat oil over medium flame. Add onions, bell peppers, and garlic. Cook until all is tender. Stir in crushed tomatoes, tomato sauce, parsley, salt, sugar, basil, oregano, and lemon juice. Cover and simmer 30 minutes. Stir in tuna and cooked elbow macaroni. Heat over low flame, five minutes. Sprinkle with parmesan cheese and serve.