There are two reasons why Italians peel peppers.  The first is that the skin is tough no matter how long the pepper is cooked.  The second, and more important, is that the skin has a bitter flavor that can permeate a dish when peppers are cooked with their skins on.

1.  Cut the pepper open by cutting along the grooves from the bottom to the top.

2.  Trim the white pith and remove the stem, core and seeds.

3.  Peel the pepper using a sawing motion with the peeler.