Preheat the broiler. Rinse the pepper and poke a hole at the ed of the pepper. Lay it on a baking sheet and broiler, turning every couple minutes, until all sides of the chill are charred, about 10 minutes. Transfer the chile to a paper bag and seal, or transfer to a bowl and cover the bowl with plastic wrap. Let the chile sit, covered, until cooled. Loosen the skin and pull off, then remove the stem and the seeds. Cut the chile into a small dice.

Heat the oil in a large skillet with a lid over medium heat. Add the potatoes and toss to coat them in the oil. Cover the skillet and cook, stirring occasionally, until the potatoes are tender, about 15 minutes.

Add the onion to the skillet and continue to cook until translucent, 5-7 minutes. Stir in the chopped chile.

Pour the eggs into the skillet and cook, stirring, until the eggs are set, 5-7 minutes. Add the cheese and continue to cook until the cheese is melted. Season to taste with salt and pepper, and serve topped with cilantro, if desired.