Cut off the tops of the jalapeÃ±os. Remove seeds if you want it to be mild! Combine all ingredients in a blender. Blend to desired consistency. That's all! As for the ingredients, I've always just sort of eyeballed the amounts. You can likely do the same, but I added more specific amounts for those of you who are a little on the safer side.
To make a chunky salsa: Blend tomatoes (without the juice), and chop up the onion and jalapeÃ±os fairly small. The onions can be a little bigger than the jalapeÃ±os. Add the onion and peppers to the blended tomatoes and add the cilantro (this time, you won't want the stems, so be sure to cut them off).