How to Make It
Heat the oil in a large pot over medium heat. Add the scallion whites, garlic, and ginger. Cook, stirring frequently, until soft, 3 to 4 minutes. Add the tomato paste and curry powder. Cook, stirring, until the tomato paste darkens, 1 to 2 minutes.
Add the coconut milk, lentils, barley, 4 cups water, and ½ teaspoon salt and bring to a boil. Reduce heat and simmer, stirring occasionally, until the lentils and barley are tender, 35 to 45 minutes (adding more water if needed to loosen).
Serve topped with the scallion greens and yogurt.