Add the tomatoes, chiles, garlic, onion, salt and water to a medium saucepan. Bring up to a boil. then reduce to a simmer and let cook until all the vegetables are fully softened, about 20-30 minutes.

Remove the pan from the heat, and use an immersion blender or food processor to pulse the mixture until it is pureed but still has some chunks in it. Transfer to a bowl and stir in the minced onion and cilantro. Taste and add more salt or thin out with water if needed. Allow to cool and serve chilled with tortilla chips or as a condiment.