Fry the chopped onion with whole cumin until the onion light golden.
Put the rest of the spices into the onion and further fry until all the spices release delicious aroma.
When the spices looking luscious, add the tomatoes in and continue cooking until you get a nice smooth sauce.
Once you're happy with your smooth looking curry sauce, put the chicken in it. Let it cook at low heat with the pan lid on until the chicken is fully cooked and tender.