Chicken and Spinach Pasta Bake

8oz uncooked rigatoni
1 tbs. Olive oil
1 cup chopped onion
1 10oz. Package frozen spinach, thawed
3 cups cooked chicken breasts cubed
114 oz. Can Italian style diced tomatoes drained
1 8 oz. Chive and onion cream cheese
1/2 tsp. Salt & pepper
1 1/2 cups shredded mozzarella

Prepare rigatoni according to pkg directions. Spread oil on bottom of baking dish, add onion. Bake at 375 for 15 minutes. Drain chopped spinach well pressing between paper towels. Stir in rigatoni, spinach, chicken and next 4 ingredients into onion in dish. Sprinkle evenly with mozzarella. Bake covered at 375 for 30 minutes remove cover and bake 15 more minutes or until bubbly.