Vegetable Tortellini Soup

Ingredients:

• 2 tablespoons olive oil
• 1 small onion, diced
• 2 cloves garlic, minced
• 2 carrots, diced
• 2 stalks celery, diced
• 2 cups chopped fresh spinach
• 4 cups vegetable broth
• 1 cup water
• 1 can (14.5 ounces) diced tomatoes
• 1 teaspoon Italian seasoning
• 1/2 teaspoon salt
• 1/4 teaspoon black pepper
• 1 package (9 ounces) refrigerated cheese tortellini
• 1/4 cup grated Parmesan cheese (optional)