- With the rack in the middle position, preheat the oven to 425°F (220°C).
- In a pot over medium-high heat, brown the onion in the butter. Add the garlic, ginger and spices. Cook for 1 minute while stirring. Add the water, lentils and sugar. Season with salt and pepper. Bring to a boil. Simmer gently, stirring often, until the lentils are tender but still intact, about 14 minutes. Add more water as needed. Adjust the seasoning.
- Meanwhile, on a non-stick or parchment paper-lined baking sheet, combine the sweet potatoes, oil and cumin. Season with salt and pepper. Bake for 15 minutes or until tender and lightly golden, stirring halfway through.
- Serve the dahl in bowls. Garnish with the sweet potatoes, cilantro and yogurt. Serve with the naan and lime wedges.
Use the finest side of a box grater to grate and effectively purée the garlic and ginger.
Pre-cut sweet potato spirals are available in the salad section of most grocery stores (along with other pre-cut vegetables, such as squash, zucchini and beets). You can replace them with julienned sweet potatoes.