Ziti Alfredo with Vegetables

Name: Ziti Alfredo with Vegetables
Ingredients: 1 medium onion, chopped; 2 garlic cloves, minced; 2 teaspoons olive oil; 8 ounces dry ziti pasta; 2 tablespoons butter; 3 tablespoons all-purpose flour; 1 cup fat-free milk; 1 1/2 cups fat-free half-and-half; 1 cup shredded Parmesan cheese; 2 teaspoons Italian seasoning; 1/4 teaspoon salt; 1 dash white pepper; 1 dash ground nutmeg; 1 (14.5 ounce) can Italian diced tomatoes, drained; 1 (10 ounce) package frozen chopped spinach, thawed and squeezed dry