Oven Baked Chicken and Spinach Pasta (Mama, what's for dinner)

8 oz uncooked gluten free rigatoni or ziti (I like Tinkyada)
1 Tbsp olive oil
1 C finely chopped onion
1 (10 oz)pkg frozen chopped spinach, thawed
3 C cooked chicken, cubed
1 (14.5 oz)can italian style diced tomatoes
1 (8 oz)container of onion and chive cream cheese
1/2 tsp salt
1/2 tsp pepper
1 1/2 C shredded mozzerella
Prepare pasta according to package directions. While pasta is cooking, spread onion and olive oil in the bottom of a 9x13 baking dish. Bake at 375 degrees F for 15 minutes or until tender. Transfer onion to a large bowl.
Drain chopped spinach well and press between layers of paper towel to remove all moisture.
Add cooked pasta, spinach, chicken and next 4 ingredients into bowl with onion. Mix well.
Spoon into baking dish and sprinkle evenly with the mozzerella cheese.
Bake, covered, at 375 degrees F for 30 minutes, uncover and bake for 15 more minutes until cheese is bubbly.