1 medium poblano chile
2 tsp. olive oil
1 medium onion, finely chopped
1 can black beans
salt and freshly ground pepper to taste
1 Tbsp. chopped fresh cilantro
Roast poblano directly over a gas flame or under the broiler as close to the heat as possible, turning frequently, until charred all over. Transfer to a paper bag; close the top, and let steam for 10 minutes.
Scrape off the skin and discard the core, seeds and ribs, and finely chop. Heat the oil in a medium nonstick skillet. Add the onion and cook over moderately high heat, stirring occasionally, until golden, about 5 minutes.
Drain beans, reserving 3 tablespoons of the liquid. Reduce heat, and add beans and the reserved liquid to the skillet. Using a wooden spoon, stir and mash the bean mixture to a rough puree. Add the poblano and stir until the beans are heated through, about 3 minutes. Season with salt and pepper. Sprinkle with cilantro to serve.