Prep: 1. Heat a grill to high heat 2. Slice potatoes in half and season with salt and pepper. 3. Chop red onions, garlic and chives. 4. In a small bowl, combine red onions with sherry vinegar and salt. Set aside to chill. 5. Whisk together oil, vinegar, mustard, garlic and 3 tablespoons of lemon juice at bottom of a large bowl. Set aside. Make: 1. Brush hot grill with oil. Place potatoes, cut side down and let them cook without moving them until nice char marks start to form. 2. Flip, add a tablespoon of lemon juice and continue cooking until roasted on outside and tender in the middle. 3. Reduce heat and cover if necessary for about 15-20 minutes total. 4. Transfer cooked potatoes to large bowl with dressing and toss to coat. Let cool and toss with arugula, onions, capers, chives and 1 teaspoon lemon zest. 5. Taste and add more dressing if needed. Serve at room temp, or make ahead and chill.
If you don't have a grill, feel free to boil or roast potatoes in oven. Check out our favorite tips for grilling here - http://blog.gatheredtable.com/2015/06/26/barbecue-basics/