Wash asparagus and break off tough ends.
Cut asparagus into 1-inch lengths.
In a large skillet, saute onion in oil until soft.
Add tomatoes, basil, pepper, and asparagus.
Simmer, partially covered, until asparagus is tender (about 20 minutes).
Meanwhile, cook noodles according to package directions.
Serve asparagus and sauce over noodles.