1. Heat oil in deep saucepan over medium heat. Add onion, pepper and garlic; cook 5 minutes, stirring occasionally. Do not brown garlic.
2. Add clam sauce and tomato paste. Partially cover pan. Simmer, stirring occasionally, for 20 minutes.
3. Spoon half of sauce over hot pasta. (Optional: Sprinkle with cheese, black pepper or hot red-pepper flakes.) Refrigerate or freeze remaining sauce for another meal. Makes 4 cups.