TO ROAST IN THE OVEN: Preheat the oven to 450 degrees F. Position racks in the upper and lower thirds of your oven. Line a large rimmed baking sheet with parchment paper.
Cut the bell peppers in half from stem down through the end. Remove the stem, membrane and seeds.
Arrange the peppers, cut-sides down on the baking sheet, making sure to leave a little space around each one so that the peppers are not crowded. If they are, divide them between two baking sheets.
Roast the peppers on the upper rack (or upper and lower racks if you have two sheets) until the tops are black and the peppers are very tender, about 25 minutes. Halfway through, rotate the pans 180 degrees (if using two pans, switch their positions on the upper and lower racks halfway through as well).
Remove the pan from the oven. With tongs or a large spatula, carefully transfer the peppers to a large mixing bowl.
TO COOK OVER A GAS STOVE TOP OR GRILL: Leave the peppers whole. Char them on all sides either directly over the gas flame, on a grill pan placed on the stove, or on an outdoor grill, until they are black all over. Transfer to a large mixing bowl.
Cover the top of the bowl with plastic wrap to allow the peppers to steam.
Let the peppers cool completely in the bowl. They’ll become slippery and even more tender.
With your fingers, slip off and discard the skins. If you charred whole peppers, slice off the stems and remove the seeds/membranes.
Slice the peppers into strips. If desired, sprinkle with a little salt, to taste.
Use the peppers right away, or transfer to a jar or similar airtight container. Store in the refrigerator as-is for up to 5 days or cover with olive oil, seal and store in oil for 2 to 3 weeks.
TO STORE: Roasted red peppers will last for about 4 to 5 days in the refrigerator in an airtight container.