How to Make It
In a large bowl, whisk the olive oil with the lemon zest, juice, garlic and sugar. Season the dressing with salt and pepper and let stand for 10 minutes.
Add the escarole, peaches, tomatoes, cucumbers and onion to the dressing and toss well. Season the salad with salt and pepper and transfer to a serving platter. Scatter the feta on top, sprinkle with the sumac and serve.
Sumac, a fruity, tart Middle Eastern spice, is available at spice shops and online from kalustyans.com.