Take a large vessel or cooking pot, fry the chopped onions in 3 tbsp oil till light brown.
Add garlic-ginger paste, red chili, turmeric powder, coriander powder, salt and finely chopped tomatoes. Cover and allow the tomatoes to tenderize.
Add the chicken and cook for another 15-20 minutes or until the chicken is fully cooked turning frequently to cook evenly.
Take 1 tbsp of oil and put in a separate frying pan. Heat and add the cubed onion, bell pepper, cubed tomato, green chili and garam masala.
Fry this for a while till the vegetables soften lightly. Do not over burn the bell pepper and other ingredients.
Add this mixture into the vessel containing cooked chicken. Mix evenly and keep stirring for another 1-2 minutes.
Serve hot with boiled rice or naan.