Mix the paprika, coriander, garam masala, cumin, chilli powder and half of the salt together in a small dish to form a flavour enhancing spice mixture.
Blend the tomatoes, yogurt, lemon juice and remaining salt together to form a rich, smooth mixture.
Heat 2 tablespoons of the oil in a large frying pan and add the chicken. Cook over a medium high heat for 3 to 4 minutes, or until sealed all over. Remove and set aside.
Reduce the heat and add the remaining oil. Add the onions, garlic and ginger and fry gently, stirring occasionally, for 3 to 4 minutes, until golden and softened. Add the spice mixture and chillies and fry, stirring continuously, for 1 to 2 minutes to release the fragrance and aroma of the spices.
Add the tomato mixture and increase the heat to bring to the boil. Reduce to a simmer and simmer for some 5 minutes or so until sauce has reduced slightly. Add the chicken and stir well.
Heat the mixture until simmering, then cook on a low heat for some 30 to 35 minutes or so or until the chicken is tender and cooked through. If the sauce becomes too thick, simply add more yoghurt.
Add the green pepper and most of the coriander (reserve some for garnish) and cook for some 10 minutes more. Taste for seasoning, garnish with coriander and serve.
This curry is also great with lamb shoulder, cubed. Just adjust cooking times upwards to 1 to 2 hours accordingly. To serve -
Serve with basmati rice and/or naan bread, chapatis and papadums.