This healthy dip recipe has a Middle Eastern twist--cucumbers, tomatoes, feta and olives are layered on top of a creamy base of hummus and a touch of tangy yogurt. A sprinkle of ground sumac adds a fruity, sour flavor. Look for this bright red spice (made from the tart red berries of the Mediterranean sumac bush) in Middle Eastern markets, specialty food shops and online at penzeys.com. Serve the dip with pita chips. Download a FREE Top 10 Appetizer Recipe Cookbook!