Place all the marinade ingredients in a medium bowl and stir to combine. Add the lamb and mix well to coat all over. Cover and place in the fridge to marinate for about 1 hour.
Line a large baking tray with kitchen foil and spray with low-calorie cooking spray. Place 8 skewers in a shallow dish of water and leave to soak for about 20 minutes. This will prevent them from burning in the oven. Preheat the oven to 220°C.
Remove the skewers from the water and thread the marinated lamb, peppers, onion and tomatoes onto the skewers to make 8 evenly-sized kebabs.
Place the kebabs on a large baking tray, spray the tops with low-calorie cooking spray and place in the preheated oven. Bake for about 25 minutes, turning halfway through, until the lamb is cooked, and the vegetables have softened.
Serve at once with basmati rice and a dollop of yoghurt, or remove from the skewers and fold inside a tortilla wrap with some yoghurt.