To roast the peppers, place them on an open gas flame and turn them frequently with tongs until all sides are charred black, 7 to 10 minutes. (Alternatively, the peppers can be roasted under a broiler or on top of a gas or charcoal grill.) Place the blackened peppers in a plastic or paper bag, seal the bag, and let stand until cool enough to handle, about 15 minutes.
Peel the peppers and remove the seeds and the stems. Chop the pepper flesh and place in a medium mixing bowl. (The chopped peppers will yield approximately 2 cups.) Add the remaining ingredients and stir to mix well. The salsa may be kept in the refrigerator for 2 to 3 days. Serve at room temperature.
Yield: about 3 cups