Place serrano peppers, garlic, and salt in a food processor; pulse until finely chopped. With the motor running, slowly pour the vinegar through the feed tube; process until sauce is smooth, about 5 minutes.
Pour sauce into a saucepan; bring to a boil and cook for 1 minute. Pour sauce into a clean jar and store in the refrigerator for at least 1 day.
Strain sauce through a fine-mesh strainer; store in the refrigerator.