Wearing plastic or rubber gloves, use a scissors or sharp knife to remove the stalk end from the peppers. Split peppers; remove and discard seeds. In a skillet, toast peppers (without oil) over medium heat for 3 to 4 minutes or until they give off a fragrance, turning once or twice with tongs.
Transfer peppers to a small bowl. Cover with hot water and soak for 30 minutes. Drain, reserving 1 cup soaking water. Place peppers in a blender container or food processor bowl.
In the same skillet, toast cumin over medium heat for 1 to 2 minutes or until it becomes fragrant, stirring often. Place cumin and olive oil in blender or food processor with peppers. Blend or process until nearly smooth, adding enough of the water the peppers were soaked in to make a medium-thick paste. Set aside.
Trim fat from meat. Place meat in a plastic bag set in a shallow dish. Spread pepper paste on both sides of steak. Close bag. Marinate in the refrigerator for 24 hours, turning occasionally.
Drain the steak, reserving marinade. Place steak on the rack of an uncovered grill directly over medium coals.* Grill to desired doneness, turning once halfway through and brushing occasionally with reserved marinade during the first half of grilling. [Allow 16 to 24 minutes for medium-rare (145 degree F) and 24 to 30 minutes for medium (160 degree F).] Discard remaining marinade. To serve, thinly slice meat across the grain. Makes 12 servings.
To test for medium heat on the grill, you should be able to hold your hand over the heat at the height of the food for 4 seconds before having to pull away.