In a small or medium saucepan, add two cups of water, chiles, tomatoes, onion & garlic. Over medium-high heat, bring the water to a soft boil, then lower heat to medium-low. Cook for 7 minutes or until tomatoes are soft.
In a blender, add one cup of the cooking water, the chiles, tomatoes, onion, garlic plus all of the spices. Puree for one or two minutes until everything is pureed well.
Note: Reserve the remaining of the cooking water for now in case the sauce becomes too thick
Add one tablespoon oil to a saucepan/skillet and heat over medium heat. Add the tomato/chile puree (careful, it will sizzle!). Turn the heat to low, and simmer, stirring often, for about 5 minutes, until the sauce darkens and thickens a little bit.
Taste and adjust salt & pepper.