Directions

1. Place anchovy fillets, mayonnaise, garlic and lemon zest in blender. Blend on setting 4 (puree) 1 minute. Add lemon juice and pulse on setting 4 (puree) for 1 additional minute. Add 3 tablespoons olive oil, 1 tablespoon at a time, pulsing on setting 4 (puree) after each addition. Refrigerate until ready to use.
2. Preheat oven to 400 degrees. Cut potatoes in half length wise and toss with remaining 1 tablespoon olive oil. Arrange on baking sheet and roast until beginning to brown and tender, about 30 minutes. Let cool slightly.
3. Combine potatoes, radish and onion in large bowl. Toss with Garlic Anchovy Dressing and top with arugula. Serve immediately or refrigerate up to 6 hours.