Chilli Powder and Indian Chilli Powder
This is where the confusion arises. In India,  chilli powder (quite naturally) refers to unadulterated ground chillies, similar to Cayenne powder. It is  powdered dried red chillies, most commonly the cayenne variety of chilli peppers but can be made of local varieties. In Indian recipes, when it asks for chilli powder, it definitely refers to unadulterated powdered chillies.