Chicken 'n' Spinach Pasta Bake

One of the reviews on this recipe said it was "restaurant" quality! 

Thanks Zaar!                                                                                                

8 ounces uncooked rigatoni pasta
1 tablespoon olive oil
1 cup finely chopped onion (about 1 medium)
1 (10 ounce) package frozen chopped spinach, thawed 
3 cups cubed cooked chicken breasts (I used chopped rotisserie chicken from the grocery deli)
1 (14 1/2 ounce) can Italian-style diced tomatoes, undrained
1 (8 ounce) container chive & onion cream cheese
2 T sun dried tomatoes
1/2 teaspoon salt
1/2 teaspoon pepper
1 1/2 cups shredded mozzarella cheese

Directions

Prepare rigatoni according to package directions.
Meanwhile, spread oil on bottom of an 11x7" baking dish; add onion in a single layer. Bake at 375 degrees for 15 minutes or just until tender. Transfer onion to a large bowl and set aside.
Drain thawed spinach well, pressing between layers of paper towels.
Stir rigatoni, spinach, chicken and next 4 ingredients into onion in bowl. Spoon mixture into baking dish, and sprinkle evenly with shredded mozzarella cheese.
Bake, covered, at 375 degrees for 30 minutes; uncover and bake 15 more minutes or until bubbly.