Gyro Salad with Tzatziki Dressing

In a large bowl, sprinkle cucumber with salt; mix well. Let stand 5 minutes. Drain. Stir in remaining dressing ingredients. Cover and refrigerate., In a large skillet over medium-high heat, cook lamb, onion and Greek seasoning until lamb is no longer pink, stirring to break the meat into crumbles; drain., Arrange salad mix on a large serving platter; top with tomatoes, cheese, olives and lamb. Spoon dressing over salad. Serve immediately with toasted pita wedges.