In a medium bowl, combine yogurt, sour cream, feta cheese, onion, lemon juice and salt. Chill, covered, for 2 to 8 hours.Advertisement
Before serving, place shredded cucumber in a fine-mesh sieve. Use the back of a large spoon or a rubber spatula to press on the cucumber to remove excess liquid. Stir cucumber into dip, then garnish with pomegranate seeds and fresh mint, snipped if desired.