In a bowl, mix together garlic powder, onion powder, salt, cumin, black pepper, oregano, paprika and brown sugar. Set aside.
Remove the membrane that's on the back side of the rib rack and discard.*
Set the rib rack onto a work surface, meat side up. Rub the Dijon mustard onto the meat side of the rack.
Sprinkle the spice rub evenly onto the mustard.
Cut the rib rack in half so that both pieces fit together into a 9 inch by 13 inch baking dish.
Set the ribs into the baking dish, meat side up.
Cover the dish tightly with aluminum foil. (Be sure to seal it all around.)
Bake the ribs for 3 hours.
Serve with potato salad.
Recipe notes:
*Use a metal spatula or butter knife to get under the membrane and start to pull it away from the meat. Then grab the membrane with a paper towel and pull it off. (Please don't use a sharp knife because you can easily slip.)