Skewer the lamb cubes on the skewers. Stir together the yogurt, olive oil and onion juice in a glass or ceramic pan or bowl and season with salt and pepper. Add the lamb skewers, coat with the marinade and refrigerate, covered, for 4 hours. Prepare a charcoal fire and let it die down a bit or preheat a gas grill for 15 minutes on low. Set the skewers on a skewer holder over the fire and grill until golden brown and succulent, turning often, about 20 minutes. Or, lacking a skewer holder, place them on the grill and grill to perfection. Serve with or on a piece grill-warmed pita bread and the cacik on the side.
CACIK (YOGURT AND CUCUMBER SAUCE)
Toss grated cucumber with a light sprinkling of salt. Leave for 30 minutes. Drain the cucumber, squeezing out all the liquid. Pound the garlic in a mortar with 1 teaspoon salt until completely mashed. Stir the garlic into the yogurt and beat with a fork until smooth. Stir in the cucumber, the dill, mint and olive oil and stir until the consistency of a thick soup. Refrigerate for an hour and serve cold.