·Sauce may be made 1 week ahead, then cooled completely and chilled, covered.
Recipe information
Total Time
1 hr
Yield
Makes about 2 1/2 cups
Ingredients
Preparation
Step 1
Rinse chiles and split open, discarding stems, seeds, and ribs.
Step 2
Heat a well-seasoned cast-iron skillet over moderate heat, then toast chiles, skin sides up, in batches, about 30 seconds (be careful not to burn them, or sauce will be bitter). Transfer chiles as toasted to a heatproof bowl and pour boiling water over them. Cover bowl and soak chiles, stirring occasionally, until softened, about 15 minutes.
Step 3
Purée chiles with three fourths of soaking liquid, reserving remainder, in a blender until smooth (use caution when blending hot liquids). Pour purée through a coarse sieve into a bowl, pressing on solids, and discard solids. Whisk reserved soaking liquid into chile mixture.
Step 4
Cook onion, garlic, cumin, and oregano in oil in a large heavy saucepan over moderately low heat, stirring, 2 minutes. Add flour and cook, stirring, 2 minutes. Whisk in chile mixture and simmer, partially covered, whisking occasionally, until reduced to about 2 1/2 cups, about 30 minutes. Season with salt, vinegar, and sugar.
