Add the yoghurt, lemon juice and marinade spices into a large bowl. Dice the chicken and add to the marinade. Cover and pop in the fridge for at 2-4 hours.
Once the chicken has marinaded, heat a large frying pan on a moderate heat. Spray with Frylight and cook the onion until soft - this will take around 5 minutes.
Add the tomato puree to the onions and cook out for a couple of minutes. Add the crushed garlic, and garam masala, cook for another couple of minutes and stir in the tinned tomatoes. Keep on a low heat.
Take the chicken pieces out of the marinade, setting the remaining yoghurt and spice mix aside. Add the chicken to a separate frying pan. Once the chicken has browned slightly on the outside add to the tomato sauce. Mix to combine and leave to cook on a low heat for 15 minutes, stirring occasionally.
Add the sliced peppers and cook for another 10 minutes or until the chicken has cooked through.
Making sure the hob is set to a low heat, stir in the remaining yoghurt marinade and fresh coriander. Leave to cook through for 5 minutes. Serve with your choice of accompaniment!