Heat a large skillet over a medium heat and add some oil. Add the diced chicken and cook until the outsides of each piece are brown. They don't need to be cooked through. 

While the chicken is in the skillet, add canned tomato sauce, onion powder, garlic paste, ginger paste, garam masala, ground cumin, ground coriander, paprika, turmeric, and salt to the bowl of a slow cooker or Instant Pot. You can also add some cayenne or red pepper flakes if you want some heat! 

Use a slotted spoon to remove the chicken from the skillet and add it to the bowl. Stir well.

Cook on high for 3 hours or low for 6 hours. (Use the Slow Cooker function if using an Instant Pot, with the Seal turned to Venting)

Stir in the heavy cream then serve, garnished with chopped fresh cilantro.