Warm Greek Pita Sandwiches With Turkey and Cucumber-Yogurt Sauce

sour cream

plain low-fat yogurt

cucumber, peeled, grated and squeezed as dry as possible

red or rice wine vinegar

garlic cloves, minced

Salt and pepper, to taste

large pitas

olive oil

large onion, peeled, halved and cut into chunky wedges

leftover roast turkey, pulled into bite-sized pieces

oregano

shredded lettuce (preferably romaine)

cherry tomatoes, halved and lightly salted