Cook ziti in a large pot of boiling water according to package directions. Drain and leave in a colander.
Heat oil in same pot. Add ground beef and onions and cook over medium- high heat, breaking up beef with a wooden spoon, 4 minutes or until beef is no longer pink.
Stir in tomatoes, garlic, Italian seasoning, salt and pepper. Bring to a simmer, cover and cook 12 minutes for flavor to develop. Stir in spinach and cook 3 minutes longer.
Remove from heat.
Heat oven to 375°F Have a 13x9-inch baking dish ready; spray with nonstick cooking spray.
Stir cooked ziti and cottage cheese into spinach sauce until blended. Spoon into baking dish. Sprinkle with cheese.
Bake 30 minutes, or until top is golden.
The last time I made this, I had some leftover cheese sauce I needed to use up so I threw it in and it was great! Made a creamier casserole that I actually preferred, but since the rest of the family likes both versions equally, I'm just addding this as a note.
Here's the cheese sauce if you're intereseted:
2 Tablespoons butter.
2 Tablespoons all-purpose flour.
1 cup milk.
1/4 teaspoon salt.
1/8 teaspoon pepper (or to taste).
1 cup Cheddar cheese.
1/4 teaspoon dry mustard.
Melt butter in heavy saucepan over low heat; add flour, stirring until smooth. Gradually add milk; cook over medium heat, stirring constantly until thickened and bubbly. Stir in salt, cheese and dry mustard.