Preheat your oven to 300°F (150°C) and line a baking sheet with parchment paper and a large piece of aluminum foil.
Remove the thin membrane from the back of the ribs by lifting a corner with a knife and pulling it off with a paper towel for better grip.
In a small bowl, combine the sea salt, black pepper, smoked paprika, garlic powder, and onion powder to create a dry rub.
Season the ribs generously on both sides with the dry rub, then wrap the rack tightly in the aluminum foil.
Place the foil-wrapped ribs on the baking sheet and roast for 2 hours until the meat is tender and starting to pull away from the bone.
While the ribs roast, whisk together the tomato paste, apple cider vinegar, maple syrup, and yellow mustard in a small bowl until smooth.
Carefully open the foil, brush the top of the ribs with the prepared BBQ sauce, and increase the oven temperature to a broil.
Broil the ribs for 3 to 5 minutes until the sauce is bubbling and sticky, watching closely to prevent burning.
Steam or lightly sauté the green beans until crisp-tender while the ribs rest for 5 minutes.
Slice the ribs between the bones and serve alongside the green beans.