1. Preheat oven to 225 C (450 F).
2. Place the peppers on a baking tray. Drizzle with half the olive oil and season with salt. Roast them for about 30 minutes until the skin is charred.
3. Next, place the peppers in an airtight container and let cool (this will facilitate peeling off the pepper skins later). Remove the skin, the seeds and chop them in chunks.
4. In a saucepan on medium high, heat the remaining olive oil and sauté onions until fragrant, about 2 minutes. Add the roasted peppers, garlic, coriander, white vinegar, and sugar and continue to cook for 1 minute. Add water and lower the heat to medium low and cook for about 30 minutes until almost all the liquid has evaporated.
5. Add cilantro. Season with salt & pepper.

Note

1. You can use any kind of green pepper you like – long hot chili, hatch chili, etc.