Preheat your oven to 275°F (135°C).
Remove the thin membrane from the back of each rack of ribs.
Rub the ribs with yellow mustard and brown sugar.
In a small bowl, combine the brown sugar, paprika, smoked paprika, black pepper, salt, chili powder, garlic powder, onion powder, and ground cumin.
Generously apply the dry rub to both sides of the ribs, pressing it into the meat.
Place the ribs on a large baking sheet lined with aluminum foil. Cover the ribs with another sheet of aluminum foil to create a sealed pouch.
Bake in the preheated oven for 2.5 to 3 hours, or until the ribs are tender.
In a medium saucepan, combine the ketchup, apple cider vinegar, brown sugar, honey, Worcestershire sauce, lemon juice, smoked paprika, garlic powder, onion powder, cayenne pepper (if using), salt, and black pepper.
Bring to a simmer over medium heat, stirring occasionally. Reduce the heat to low and simmer for 15-20 minutes, or until the sauce has thickened.
Preheat your grill to medium-high heat.
Remove the ribs from the oven and discard the top layer of aluminum foil.
Brush the ribs generously with the barbecue sauce.
Place the ribs on the grill and cook for 5-10 minutes, basting with more sauce and turning occasionally, until the ribs are caramelized and slightly charred.
Remove the ribs from the grill and let them rest for a few minutes before slicing.
Enjoy your meal!