Put chile peppers and onion into a pan with water and bring to a boil.

Dump into a colander and let it cool a bit so you can remove any stems and the seeds of the anchos.

Put chile peppers and onions in a food processor or blender and add 2 cups of the water, garlic and salt.

Put a fine-mesh sieve over a bowl and press thru then scrape the outsides of the sieve to get as much as you can.

Stir in the remaining water and vinegar.

Stir well.