Cut a medium sized onion into halves. Remove flaky skin and first thin layer. Separate the rings in preparation for the food processor. Yellow or white onions may be used. The yellow variety will provide a slight sweetness to the dish.
Scallions can also add an interesting twist.
In a food processor, blender, or hand held dicer, chop the onion and peppers. Ideally, the end result will be a coarsely ground mixture of the ingredients included thus far. Remove the stems from the cilantro. Add the remainder of the bunch to the blender or processor. You will need to chop the cilantro with a sharp knife if you are preparing by hand and stir it into the salsa mixture.