Using your fingers, pull and remove those thin papery skins on each baby back ribs.
In a small medium-sized bowl, combine the chili powder, garlic, paprika, salt, cayenne, mustard, sugar and cumin then mix it well.
Using mixture, rub all over the ribs with it then cover and refrigerate overnight.
After that, preheat the oven to 250°F.
Put the ribs meat side up in one layer on another sheet pan then bake it until tender for up to 4 hours.
Remove the ribs from the oven 30 minutes before they are done and brush them with your favorite barbecue sauce. Bake again until tender and serve with additional sauce on the side or a piece of bread.