Preheat your griddle to medium-high heat.
Prepare the rub: Combine brown sugar, paprika, chili powder, onion powder, garlic powder, and black pepper in a small bowl. Generously coat both sides of the ribs with the rub.
Sear the ribs: Place the ribs on the hot griddle, meaty side down. Sear for 3-4 minutes per side, or until nicely browned.
Create the foil tent: Tear off a large sheet of aluminum foil and fold it in half to create a double layer. Pour about 1/4 cup of apple cider vinegar onto the center of the foil. Place the ribs meat-side up on the foil, then fold the sides up and around the ribs to create a sealed tent.
Steam and sauce: Reduce the heat to medium-low and cover the griddle with a lid. Steam the ribs for 45-60 minutes, or until tender and falling off the bone. Check on them occasionally and add more vinegar if needed to keep the bottom moist.
Glaze it up: In a small bowl, whisk together honey and Dijon mustard. Carefully remove the foil and brush the ribs generously with the glaze. Increase the heat to medium-high and return the ribs to the griddle, open-faced. Cook for 2-3 minutes per side, caramelizing the glaze and creating a sticky, delicious coating.
Rest and serve: Transfer the ribs to a cutting board and let them rest for 5-10 minutes before slicing and serving. Enjoy with your favorite BBQ sauce, if desired.