Cover chiles with warm water and let stand for about 30 minutes or until softened; reserve and strain the liquid as you drain it from the anchos. Remove stems, seeds, and membranes from chiles.
Sauté onion in oil until tender; toss in garlic and sauté when onions are just about tender. Stir in chiles, 2 cups reserved, strained chile liquid, and the remaining ingredients. Heat to boiling; reduce heat. Simmer uncovered for 20 minutes; cool.
Pour into a food processor or blender, cover and puree until smooth. Cover and refrigerate for up to 10 days.