Preheat your oven to 300°F (150°C).
In a small bowl, combine the smoked paprika, garlic powder, sea salt, and black pepper to create a dry rub.
Pat the beef brisket dry and coat all sides thoroughly with the spice rub.
Place the brisket in a roasting pan, cover tightly with foil, and roast for 3-4 hours until the meat is tender and easily pulls apart.
While the meat rests, thinly slice the yellow onion.
Heat the olive oil in a skillet over medium-low heat. Add the onions and cook slowly for 20 minutes, stirring occasionally until they are deep golden brown.
Deglaze the onion skillet with apple cider vinegar, scraping up any browned bits from the bottom.
Steam the green beans for 5-7 minutes until they are tender-crisp and vibrant green.
Slice the brisket against the grain and serve topped with the caramelized onions alongside the steamed green beans.