Mix the olive oil, Bharat spice mix, ground cumin, sumac and salt at the bottom of a large bowl, add the chicken to it and mix to coat. You can either marinade for 30 minutes or cook immediately if short on time.
Spread the seasoned chicken on a baking tray and cook in the preheated to 200C/400F oven for 30 minutes, then move up and cook under a grill/broiler for 2 minutes to crisp it up a bit.
Once the chicken went into the oven, start on the onions. Slice them, then pour the olive oil in a large saucepan and add the pine nuts and cook them until lightly toasted for about 1-2 minutes depending on how hot the oil is, then remove the pine nuts with a slotted spoon from the oil and put them a bowl.
To the same oil add the sliced onions, cook over low heat for 20 minutes or until they are very soft, then add the sumac, cumin and black pepper, stir to combine and take off the heat.
Slightly toast the flatbread in the oven to avoid it going soggy. Then top each flatbread with sumac flavoured onions and chicken, drizzle the juices collected at the bottom of the baking tray all over and sprinkle with the pine nuts. Serve with plain yogurt on the side.