Adjust the oven shelf to be about 2 inches from the broiler. Turn the broiler to high. Allow time for the broiler to arrive at a high temperature; otherwise, the tomatillos will get soggy before being roasted. If using a grill, make sure your fire is very hot.
Peel away the papery brown husk on the outside of the tomatillos. Dispose of the husks. Rinse the small fruits under warm running water to remove any of the natural gum left on the skin. With a small knife, remove the core like you would a tomato. It is not necessary to take out the seeds. Cut tomatillos in half, if desired.
Place tomatillos on a broiler pan rack and place under the broiler, and cook them for about seven minutes until they're soft and slightly charred, turning them once. If using a grill, watch carefully and turn several times. The goal is to let the skins get a little bit black in some areas; this gives your recipe the subtle taste of smoke.
Set aside tomatillos until they are cool enough to handle. Proceed with your salsa or other recipe.