Preheat your oven to 325°F (165°C).
Season the brisket with salt and pepper on all sides.
Heat oil in a large oven-safe pot or Dutch oven over medium-high heat.
Sear the brisket on all sides until browned, about 4-5 minutes per side. Remove and set aside.
In the same pot, add chopped onions and sauté until softened.
Add garlic and cook for another minute until fragrant.
Stir in the sauce ingredients (such as vinegar, sugar, ketchup, or any other you use).
Return the brisket to the pot, spoon some sauce over the top, and cover with a lid.
Place the pot in the oven and braise for 3 to 4 hours, until the brisket is tender.
Check occasionally and spoon sauce over the meat to keep it moist.
Once done, remove the brisket and let it rest for 10 minutes before slicing.
Serve with the braising sauce spooned over the top.