Chicken 'n' Spinach Pasta Bake

INGREDIENTS

• 8 ounces uncooked rigatoni
• 1 tablespoon olive oil
• 1 cup finely chopped onion (about 1 medium)
• 1 (10-oz.) package frozen chopped spinach, thawed
• 3 cups cubed cooked chicken breasts
• 1 (14.5-oz.) can Italian-style diced tomatoes
• 1 (8-oz.) container chive-and-onion cream cheese
• 1/2 teaspoon salt
• 1/2 teaspoon pepper
• 1 1/2 cups (6 oz.) shredded mozzarella cheese