8 ounces thin spaghetti
1 tablespoon olive oil
2 cups chopped onion
2 teaspoons minced garlic
1 teaspoon dried oregano
1/2 teaspoon celery salt
1/4 teaspoon crushed red pepper
1/4 teaspoon freshly ground black pepper
1/4 teaspoon crushed saffron threads (optional)
8 ounces extra-lean ground beef
1 2/3 cups lower-sodium marinara sauce (such as Amy's)
2 ounces pimiento-stuffed olives, sliced (about 1/2 cup)
1/4 cup dry sherry
1 tablespoon capers
1/4 cup chopped fresh parsley, divided