Cook pasta according to package directions.
Whirl together arugula, zest, garlic, 1/4 cup walnuts, the oil, salt, and pepper in a food processor until blended, scraping inside of bowl as needed.
Drain pasta, reserving about 1/4 cup of the water. Return pasta to pot and add pesto, stirring to coat. Stir in remaining walnuts, the cheese, raisins, and reserved pasta water.
Note: Nutritional analysis is per 1 1/2-cup serving.
* Percent Daily Values are based on a 2,000 calorie diet. Your daily value may be higher or lower depending on your calorie needs.