Serves 8 INGREDIENTS 1 tablespoon plus 1½ teaspoons tamarind concentrate ½ cup warm water 3 tablespoons canola oil ½ cup unsalted peanuts (preferably unroasted), roughly chopped 1 tablespoon mustard seeds 16 curry leaves, roughly torn (optional) 6 dried red chiles (optional) 1 teaspoon cumin seeds ¾ teaspoon turmeric 1 large red onion, quartered and thinly…