1 cup balsamic vinegar
2 cups molasses
1 tablespoon freshly ground black pepper
21/4-pound tri-tip beef roast, trimmed
Combine the vinegar, molasses and black pepper in a medium saucepan. Bring to a boil, then reduce heat to low and simmer until the sauce is reduced by one third. (You should end up with two cups of sauce.)
Season the beef with kosher salt and place on a preheated grill. Brush the sauce onto the meat, then flip it and brush the other side. Cook for 3 to 4 minutes, then flip again and brush on more sauce. Continue this process every 3 to 4 minutes until a thermometer inserted into the center of the meat registers 135 degrees for medium-rare, about 30 minutes total. Transfer to a cutting board and let rest 10 minutes before slicing. Serves 6.