In a skillet, pour in some oil and heat it up.
Add cumin seeds and allow them to pop for a few seconds.
Then, toss in whole garam masala and let it sizzle for another 3 to 4 seconds.
Immediately add thinly sliced onions and sauté until they turn a lovely pink color.
Once the onions are ready, add the marinated chicken.
Stir and cook on high heat until the chicken changes color.
Now, add green chilies and diced tomatoes.
Cook until the tomatoes blend into the gravy and the oil rises to the top.
Next, pour in ½ liter of water and mix everything well.
Allow the chicken to cook for 30 minutes on medium to low heat until it becomes tender.