In a large skillet, heat the oil and saute the onion until translucent.
Add the cumin seeds and saute for 30 seconds.
Add the garlic and fry for 15 seconds until fragrant.
Now add the chicken, and cook on medium high heat for 3-4 minutes or until the chicken has changed color.
Now add the salt, chicken cube, and the other spices.
Cook for 5-7 minutes on medium high heat, while stirring, or until you can see the oil separating from the curry.
Add the green chillies and the crushed tomatoes, stir, and cover the skillet. Lower the heat to low, and cook for 10 minutes.
Remove the lid, and add the sliced bell capsicum and onion.
Cook for 2 minutes to let the flavours blend. Serve with rice or naan.