In a bowl, combine ALL spices, except the sugar and the pepper flakes, and mix together thoroughly.
Add the mustard, and mix the spices into the mustard, until it's almost a paste.
Take your rack of ribs, and sprinkle the bone side with a little cajun seasoning.
On the meat side of your ribs, spread the mustard/spices, almost like you were icing a cake. Cover entire meat side with your mustard/spice mixture.
After the ribs are covered, sprinkle your pepper flakes on top, to add a little spice. Finally, sprinkle your sugar on top, to get that little twinge of sweetness!
Smoke on a charcoal BBQ, for about an 1 hour and 30 minutes, bone side down the entire time. Adjust cooking time depending on how big your rack of ribs is, and how hot your fire is. The key to these ribs being perfect is low and slow.