Preheat oven to 300°F.
Rub the beef brisket evenly with smoked paprika, garlic powder, onion powder, sea salt, and black pepper.
Place the brisket in a baking dish, cover tightly with foil, and roast for 3 to 4 hours until fork-tender.
While the brisket rests, thinly slice the yellow onion.
Heat olive oil in a skillet over medium-low heat and add the sliced onion.
Sauté the onion for 20 minutes, stirring occasionally, until deeply caramelized and golden brown.
Stir in the apple cider vinegar to deglaze the pan and scrape up any flavorful browned bits.
Steam the green beans for 5 minutes until they are vibrant and tender-crisp.
Slice the brisket against the grain and serve topped with the caramelized onions and a side of green beans.