This curry has no added liquid; instead, it relies on the onion’s liquid to create its sweet magic. Bottle masala boosts this to a completely new level, but if you don’t have any, use the less complex English-style Madras curry powder.
2 medium-size red onions, cut in half lengthwise and thinly sliced
Heat the oil in a large skillet over medium heat. Add the onions and bell pepper, stir once or twice, and cover the skillet. Cook, stirring, until the onions turn caramel brown with a deep purple hue and appear very soft, 25 to 30 minutes. (Stir occasionally at first, but once the onions cook down and the liquid evaporates, stir more frequently.)