Marinate the chicken in turmeric, salt and lemon juice for about 30 minutes.
Heat 1 tbsp. oil in a pan and sear the chicken till brownish on the outside. This takes about 10 minutes.
Now heat the remaining oil in a pan/kadhai. Add cumin seeds and allow to sputter.
Now add sliced onions, ginger and garlic pastes and bhuano (saute) on low flame till golden brown and the ginger-garlic loses its raw smell. This is a slow process that must be done on low heat to bring out maximum flavour.
It took me about 15-20 minutes. If the masala gets too dry or sticks to the bottom, add 1-2 tbsp. of water.
Add chopped tomatoes with pepper and cook everything till tomatoes are mushy. Takes about 5-7 minutes. Cool it and blend to make a thick paste.
Add the masala paste with chicken pieces back to your pan. Add some water to make the curry runny.
Add garam masala, chicken masala, cayenne (optional). Cook for 15 minutes on low flame or till the chicken is cooked and tender. Taste and adjust seasoning.
Your chicken curry is ready. Serve with hot rotis or rice.