Make a fine paste by grinding together chopped onion, chopped ginger, chopped garlic, and green chilies.
Heat oil in a saucepan and add cumin seeds and all the whole spices. Once they start to splutter, add the ground onion paste. Cook till the paste turns light brown and starts to separate from the oil.
Now add chopped tomatoes, turmeric powder, red chili powder, and coriander powder. Cook till the tomatoes are soft and everything looks well combined.
Add marinated chicken pieces, garam masala powder, salt, and 1 cup of water. Stir well and add salt if needed. Cook on medium to low heat for 20 minutes or till the chicken is fully cooked. Remove from heat.