Source: Everyday Food, June 2010, marthastewart.com
1 small white onion, sliced crosswise into 1/2-inch-thick rounds
2 tablespoons vegetable oil, plus more for grill
1/4 cup fresh lime juice (from about 3 limes)
2 tablespoons roughly chopped fresh cilantro
Coarse salt and ground pepper
Heat broiler, with rack in top position. Place poblanos and onion on a rimmed baking sheet and broil until charred, 7 to 10 minutes, flipping halfway through. When poblanos are cool enough to handle, rub with a paper towel to remove skins. Remove stems and seeds and discard. Roughly chop poblanos and onion and place in a medium bowl. Stir in oil, lime juice, and cilantro; season relish with salt and pepper.