Toss the drumsticks in a large bowl with a tablespoon of the oil, 2-3 tablespoons of the yogurt and all of the spices and seasonings.
Leave to marinate for 30 minutes or, at this point the chicken mixture can marinate in the refrigerator overnight.
Preheat the oven to 375ºF.
In a casserole large enough to hold both the chicken and the potatoes without crowding, add the potatoes with the remaining oil and season with salt and pepper.
Add the chicken drumsticks and bake for about 45 minutes, until cooked through and golden.
Serve with the onions, tomatoes and cilantro scattered over. Serve remaining yogurt on the side