1. In a large pot, heat some oil over medium heat. Add the chopped onion and cook until translucent.
2. Add the minced garlic and ginger, cooking for another minute.
3. Stir in the curry powder, ground cumin, and ground turmeric. Cook for another minute to release the spices' aromas.
4. Add the diced sweet potatoes, red lentils, coconut milk, and vegetable broth. Bring to a boil, then reduce heat and let simmer for about 20-25 minutes, until the lentils and sweet potatoes are tender.
5. Season with salt and pepper to taste. Serve hot, garnished with fresh cilantro.