PreHeat oven to 350 degrees
Cook beef & onion in lge saucepan, stirring occasionally, until beef is no longer pink. Add water.
Layer ingredients as follows in ungreased 13x9 baking dish: 1/2 pasta, 1/2 sauce & 1/2 cheese. Repeat layers; cover.
Bake for 20 to 25 minutes or until heated thgrough and cheese is melted. Season with salt.
For Freeze Ahead:
Prepare as above; do not bake. Cover;freeze for up to 2 months. Thaw overnight in refrigerator.
Preheat oven to 350 degrees.
Bake for 45 to 55 minutes or until heated through and cheese is melted. Season with salt.