Brown Sweet Potato: In a large pot, over medium heat, heat 1 tbsp coconut oil. When the pot is hot, add the sweet potatoes. Season with salt and pepper. Cook for 6-8 min, stirring occasionally, until browned. Transfer to a bowl and set aside. The sweet potatoes will finish cooking in another step.
Cook Onion: To the same pot, add the remaining coconut oil. Reduce heat to medium-low. Add the onions. Cook for 4-6 min, stirring often, until tender.
Add Garlic & Ginger: Add the garlic and ginger. Cook for another 2-3 min, stirring occasionally. If you're using fresh diced tomato, add it now, if you're using canned diced tomatoes, add with the liquids.
Add Spices: Add the curry paste, turmeric, cumin, coriander and garam masala. Cook for another 1 min, stirring constantly, until fragrant, to toast the spices.
Add Liquid, Lentils & Sweet Potato: Add the coconut milk, broth or water, lentils and reserved sweet potatoes. If you're using canned diced tomato, add those now. Season with a pinch of salt. Bring to a boil over high. Once boiling, reduce heat to low and maintain a gentle simmer. Cook for 20-25 min, stirring occasionally, until the lentils and sweet potato are tender.
Add Seasonings: Stir in the lime juice and chopped cilantro, reserving a little cilantro for topping.
Serve with cooked rice, naan, lime wedges and toasted coconut flakes, if desired. Garnish with fresh cilantro.