Cooking Directions:
1. Cook pasta according to package directions; drain.
2. Preheat oven to 350ºF.
3. In a medium saucepan, melt butter. Stir in flour. Gradually stir in milk. Cook, stirring constantly over medium heat, until sauce thickens. Stir in salt and pepper. Add onion and cheese; stir until cheese melts. Stir cheese sauce into pasta.
4. Spoon into a greased 2-quart baking dish. Top with bread crumbs. Bake 30 minutes, or until bread crumbs are golden brown.