Combine first 9 ingredients and marinate overnight.
Saute the onion in the butter until soft. Add marinated chicken and cook about 10 minutes. Add the tomato sauce and diced tomatoes. Cook for 30 minutes over medium-low heat with the lid on. Add the whipping cream (I have used light cream or half-and-half also) and cilantro just before serving over Basmati rice.
Note: this is a little spicy, but you can cut back on the cayenne if you want.
I'm also hoping to work on something crafty for Penny this week... Hooray for not being sick!