Cook pasta according to package directions.
Combine clams, broth, onions and orange zest in a large skillet over medium-high heat. Bring to a simmer and simmer 5 minutes.
Toast bread crumbs in a small, dry skillet over medium heat. Drain pasta, adding 1/2 cup of cooking water to clam mixture in skillet. Simmer 1 minute.
Place pasta in a large serving bowl. Pour over clam mixture and top with toasted bread crumbs.