Chicken & Spinach Pasta Bake

• 8 oz uncooked rigatoni
• 1 T olive oil
• 1 c chopped onion
• 1 (10 oz) pack frozen spinach, thawed
• 3 c cubed, cooked chicken breasts
• 1 (14 oz) can Italian-style diced tomatoes, drained
• 1 (8 oz) container Philadelphia chive & onion cream cheese
• ½ t salt, ½ t pepper
• 1½ c shredded mozzarella cheese

Prepare rigatoni according to pkg directions.