In a pan on high heat add oil and onions and fry until translucent.
Immediately add the ginger-garlic paste, saute for 30 seconds.
Add chicken and saute for 10 minutes. The color of the chicken will turn white and then have some browning.
Add the above karahi masala and mix for 30-45 seconds or until all the chicken is coated with it.
Now add the tomato puree and saute until the oil separates (takes 2-3 minutes).
Add 1/2 cup water, cover the pan and lower the heat slightly and cook for 10-15 minutes or until the chicken is fully cooked.
Finally add the lemon juice and cilantro leaves and turn off the heat.
Let it sit covered for 1 minute before serving. Serve and enjoy.