Directly over a stovetop gas flame, or on a foil-covered baking sheet placed under the broiler or in a 450 degrees oven, roast the bell peppers, turning occasionally with tongs, until blistered and charred all over, about 10 minutes for the stovetop and broiler or 30 minutes for the oven. Immediately transfer the charred peppers to a large bowl, cover tightly with plastic wrap and let cool for 10 to 15 minutes.
Using paper towels or the backside of a paring knife, rub the skin off the peppers. Cut out the stem and seeds and discard. Rinse the peppers if desired.