Preparation

• Separate the stems from the chard leaves. Coarsely chop the leaves and slice the stems crosswise 1/2 inch thick.
• Heat the oil in a 4- to 5-quart heavy-duty pot over medium-high heat. Add the mustard, cumin, and coriander seeds, stir to coat, and then cook until the mustard seeds begin to pop, about 1 minute. Turn the heat down to medium low and stir in the ginger, garlic, turmeric, and cardamom. Cook, stirring, until fragrant, about 2 minutes.
• Add the chard stems, onion, and jalapeño, and cook, stirring occasionally, until the onion is translucent, about 5 minutes. Add the rhubarb, lentils, brown sugar, 2 tsp. salt, and 5 cups of water. Bring to a boil and then simmer for 30 minutes. Add the chard leaves. Continue to simmer until the lentils are tender but not falling apart, about 5 minutes more. Season to taste with salt and brown sugar. Serve topped with a dollop of Greek yogurt and the cilantro.