Chicken 'n' Spinach Pasta Bake

INGREDIENTS

• 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 (I used 10 oz. fresh baby spinach leaves, chopped)
• 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
• 1/2 teaspoon salt
• 1/2 teaspoon pepper
• 1 1/2 cups shredded mozzarella cheese