Combine all ingredients except the sugar in a 2-qt. saucepan; boil. Reduce heat; simmer for 10 minutes.

Meanwhile, cook sugar in a skillet over medium-high heat until it becomes dark amber and syrupy, about 5 minutes. Add caramelized sugar to vinegar mixture and whisk to combine; cook sauce for 5 minutes; transfer sauce to a glass jar with a tight-fitting lid.

Refrigerate, covered, for 3 weeks; strain to remove solids; return to jar. Refrigerate for up to 8 months.

MAKES ABOUT 2 CUPS