On an open flame: Hold the pepper with tongs over the fire; cook, turning, until all sides are charred and blistered.
Under a broiler: Slice peppers in half lengthwise; then arrange, cut side down, on a baking sheet lined with foil. Set an oven rack to the uppermost position and broil the peppers until blackened and blistered.
Remove the peppers from the heat, place in a zip-top bag, and seal. Let sit 5 to 10 minutes, or until the steam loosens the skin. Use a knife and fork to gently remove seeds and skins.