In a mixing bowl, add all BBQ rub ingredients and mix well.
Remove membranes from spare ribs, if desired, and trim any excess fat. Season heavily on both sides. Allow to sit out for 30 minutes to let seasoning "sweat" into meat.
Heat smoker to 275 degrees, with your favorite wood for smoke and flavor. I recommend apple, but any will do well.
Place ribs on grill, bone side down.
While ribs are smoking, prepare BBQ Sauce.
In a medium pan over medium high heat, melt butter and add onions. Cook for 3-4 minutes or until turning translucent. Add garlic and cook for additional 2 minutes. Add remaining ingredients and bring to a boil while whisking. Immediately reduce to a simmer and allow to cook for 10-15 minutes.
Remove from heat and allow to cool.
After 3 1/2 hours, start testing ribs for doneness. Test by moving the bones in the ribs to see how much "give" they have. Bones should be exposed from meat by around 1/2 inch, and should give slightly but not pull away from the meat. When done, slather both sides with sauce, pull ribs and allow to rest lightly tented in foil, for 5-10 minutes.
Slice, and enjoy!