01 -
Set oven temperature to 275°F.
02 -
Mix ketchup, onion soup mix, and water in a large bowl until well combined.
03 -
Place brisket in roasting pan, pour sauce over, flip to coat both sides.
04 -
Seal pan tightly with foil, keeping it from touching meat and sauce.
05 -
Roast for 7-8 hours until fork tender but not falling apart.
06 -
Let rest 1-2 hours before slicing against grain into 1/2-inch pieces.