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