Heat 2 tbsp butter in a pan and while the butter is melting, add in all the spices at one time (i.e. chilli powder, coriander powder, cumin powder, kasuri methi, garam masala powder, turmeric powder, salt, and pinch of sugar). Add brown onion or onion powder, mix well. Add tomato puree and tomato ketchup and combine all the ingredients well together. Cover the pan with a lid and cook the sauce for 1 minute or until the butter oozes out. Remove the lid and add cream little by little stirring continuously or else it will get curdled. Mix well. Switch off the flame. The silky butter sauce is ready.