Combine all of the ingredients in a blender and blend until smooth. Transfer to a nonreactive saucepan and simmer for 20 minutes to allow the flavors to marry. Use immediately, or refrigerate in a nonreactive, airtight container for up to 2 weeks.
Place the ribs on a large baking sheet. In a small mixing bowl, combine the kosher salt, brown sugar, paprika, garlic powder, onion powder, cumin, black pepper and cayenne. Stir well to combine.
Divide the mixture evenly between the racks and rub well onto all sides. Wrap the ribs in 2 layers of plastic wrap. Allow to sit undisturbed for at least 20 minutes, and up to 8 hours before proceeding. (Refrigerate if ribs sit longer than 20 minutes.) Remove the ribs from the refrigerator and allow to come to room temperature for 1 hour. Prepare a stovetop smoker according to the manufacturer's instructions. Remove the plastic wrap and place the ribs on the rack in the stovetop smoker. Close the lid and smoke for 1 hour over low heat.
Preheat the oven to 275 degrees F.
Remove the ribs from the smoker and place on a foil-lined baking sheet. Generously brush the ribs on both sides with the sauce and cover with aluminum foil. Bake for 2 hours. Remove from the oven and allow to rest, covered, for 20 minutes.
Using a sharp knife, slice between the ribs and serve, with additional sauce on the side.