Cook pasta according to package directions. Meanwhile, in a large skillet, saute asparagus and onion in butter for 5-8 minutes or until asparagus is crisp-tender., Add the ham, cream, pepper and salt; bring to a boil. Reduce heat; cook over low heat for 1 minute. Drain pasta. Add to the asparagus mixture; toss to coat. If desired, top with shredded Parmesan cheese.