Put the bell peppers on the baking sheet and roast for 35 to 40 minutes, turning them occasionally, until the outer skin is blackened. Once the peppers are roasted, transfer them to a heat-safe bowl and cover the bowl with a lid or a
silicone cover. Let the peppers sit for about 30 minutes. The outer skins of the peppers slide right off if you let them steam inside a bowl for a little while (see note 4). Once the peppers are cool enough to handle, remove the skin, stem, seeds and ribs.