Remove the membrane from the back of the ribs and pat dry. (Note: I do not remove the membrane but if you want to, now is the time)
Rub a thin layer of mustard over both sides of the ribs.
Mix the dry rub ingredients together and coat the ribs evenly.
Place ribs meat side up on a foil-lined baking sheet.
Tightly wrap the ribs in foil.
Bake for 2½–3 hours, until the ribs are tender and the bones begin to loosen. (All ovens are different. I bake it for exactly 2½ hours every time and it comes out perfectly.)
Remove ribs from foil and brush with barbecue sauce.
Return ribs to the oven uncovered and bake 10–15 minutes at 425°F to set the sauce.
Rest the ribs for 10 minutes.
Slice between the bones and serve.
Notes
To remove the membrane: Gently slide a knife under the membrane, then use your fingers to slowly peel it away from the bones. If it's too slippery to grip, you can use a paper towel or a kitchen towel to grab it.
Don't add the BBQ sauce too early. It can get burnt and bitter if it cooks too long. You want to add it towards the end, then put the ribs back in the oven so the sauce can get sticky and caramelized.
If you don't like mustard as the binder, you can use oil, butter, or hot sauce instead. Its primary purpose is to help the dry rub stick to the meat.
To verify the ribs are done, use an instant thermometer between the bones. Don't touch the bones or you'll get an inaccurate reading!