Place rice in a strainer and rinse under cool water until water runs clear. Transfer to a medium pot. Cook rice over medium-low heat, stirring gently, until fragrant and toasted, 3 to 5 minutes. Add 4 cups water and salt, cover and bring to a boil. Reduce heat to medium-low and simmer, covered, until water is absorbed, about 1 hour. Uncover pot, fluff rice and set aside.
Meanwhile, simmer the lentils in 3 cups water, partially covered, for 20 minutes. Add tomato, onion, garlic, curry powder and salt. Simmer for 30 minutes more, covered, until lentils are tender. Serve over rice. Top with cashews and a dollop of yogurt.