Preheat your oven to 350°F. While the oven is preheating, work on removing the membrane off of the back of each slab of ribs. Use a knife to just loosen up that white membrane, and then use your hands to pull it off in one piece. Using a paper towel to grip it may help.

Lay out two pieces of aluminum foil that are large enough to wrap around each slab of ribs (they will be wrapped separately). Place one slab of rib on each piece of foil. Pat the ribs as dry as possible with a paper towel. 

Using gloved hands, add the brown sugar, cajun seasoning, garlic powder, onion powder, and black pepper to a bowl. Mix it up until everything is evenly combined. 

Slather one tablespoon of the yellow mustard all over each slab of rib. Now sprinkle the seasoning mixture evenly over each slab of ribs, on the front and back. Use your hands to massage the seasoning into the ribs.

Make sure the ribs are “meaty” side up, rib side down on the piece of foil. Now tightly wrap the foil around each slab, and place it on a baking sheet. Put the baking sheet in the preheated oven. 

Cook the ribs for one and a half hours and remove them from the oven. Unwrap the foil (keep the ribs on the foil, just unwrap it), drain any excess juices from the foil by using a spoon, or gently pour it into a temperature proof bowl. 

Slather your favorite barbecue sauce all over each slab of ribs. Place the baking sheet back into the oven and cook for an additional 30-45 minutes to help the sauce get some color and adhere to the ribs. 

Remove the baby back ribs from the oven and let them sit for at least 10 minutes before cutting. Use a very sharp knife, or an electric knife and cut them in between each rib. Serve with additional bbq sauce if desired.