Bring 1 cup water to a boil in a small saucepan and add chiles, onion, and garlic. Cover, then reduce heat and simmer until chiles are very tender when pierced, about 15 minutes.
Whirl chile mixture in a food processor with vinegar and salt until fairly smooth.
Servings 0
* Percent Daily Values are based on a 2,000 calorie diet. Your daily value may be higher or lower depending on your calorie needs.