Soak 8 wooden skewers in water. Thread lamb onto skewers and arrange in an appropriate sized container with sealable lid. Combine onion, lemon juice and oil in a small jug, season well with McCormick Sea Salt and Black Pepper and pour over the lamb to coat well, ensuring lamb is covered. Cover and place in refrigerator to marinate for 2 hours or overnight.
In a small bowl combine yoghurt and McCormick Garlic Powder, cover and set aside in refrigerator.
In a small saucepan, place passata, McCormick Paprika and Hot Chilli Powder and simmer for 20 minutes. Remove from heat and set aside keeping warm.
Preheat BBQ or large frying pan over high heat. Cook lamb skewers, turning occasionally, for 10 minutes until brown and cooked through.
To serve; divide the bread, tomato, chillies, lettuce and tabouli among serving plates. Top with lamb skewers and drizzle over heated passata and garlic yoghurt sauce.
This marinade combined with 500g of minced lamb shaped into koftas, would make a great substitute for lamb back strap.