Gather the ingredients.
Heat the oven to 325 F. Line a shallow baking pan with foil; coat the foil with oil or spray with nonstick cooking spray.
In a small bowl, combine the Cajun seasoning ingredients. Mix well.
Pat the country-style ribs with paper towels to dry.
Rub 1 tablespoon of the Cajun seasoning mixture over all sides of the ribs. (Reserve the rest of the seasoning mixture for other uses.)
Arrange the ribs in the prepared baking pan and then top with onion slices.
Cover with another piece of foil and bake in the preheated oven for 1 hour and 15 minutes, or until the ribs are very tender.
Remove the top piece of foil and brush the ribs with barbecue sauce.
Bake uncovered for about 15 minutes longer, or broil for about 2 to 3 minutes for a crisper exterior.
Serve and enjoy.