Bring a small amount of water to a boil and add the dried chile peppers. Cook for 2-3 minutes, or until softened.
Roast the tomatoes, serrano peppers, and onion on a hot pan until they turn brown and look slightly burnt.
Remove the chile peppers from the water and add to a blender with the rest of the ingredients and blend for about 20 seconds for a thicker salsa, or longer for a smoother salsa.
Serve with tortilla chips or as part of another recipe.