Heat the broiler to high and arrange a rack in the upper third of the oven. Place the bell peppers directly on the rack. Roast, turning occasionally, until they blacken and blister on all sides, about 20 minutes. Remove the peppers from the oven and place in a heatproof bowl. Cover tightly with plastic wrap or a baking sheet and let sit for about 30 minutes. When the peppers are cool enough to handle, remove their skins and slice them open. Remove the seeds and membranes and discard. Slice the peppers into 1/2-inch-thick strips and season with salt and pepper. If not using immediately, refrigerate for up to 4 days in an airtight container. Serve with mahram sauce