STEP 1 :
Preheat oven to 350°. Break spaghetti into thirds; cook according to package directions for al dente.
STEP 2 :
Meanwhile, in a Dutch oven, cook beef over medium heat 6-8 minutes or until no longer pink, breaking into crumbles; drain. Stir in taco seasoning and water; bring to a boil. Reduce heat; simmer, uncovered, 5 minutes, stirring occasionally.
STEP 3 :
Stir in beans, tomatoes, 1 cup cheese and salsa. Drain spaghetti; add to beef mixture and toss to combine.
STEP 4 :
Transfer to a greased 13×9-in. baking dish. Bake, covered, 20 minutes. Sprinkle with remaining cheese. Bake, uncovered, 3-5 minutes longer or until cheese is melted. Let stand 5 minutes before serving.
Cool unbaked casserole; sprinkle with remaining cheese. Cover and freeze. To use, partially thaw in refrigerator overnight. Remove from refrigerator 30 minutes before baking. Preheat oven to 350°. Bake casserole, covered, 55-60 minutes or until heated through and a thermometer inserted in center reads 165°.