Heat the olive oil in a large pot over medium heat. Add the onion and sauté for about 5 minutes, until translucent. Add the garlic and ginger and sauté for another minute, until fragrant.
To the pot, add the tomato paste, cumin, coriander, turmeric, cinnamon and cayenne pepper. Stir into the onion mixture, then pour in the broth and stir. Scrape any stuck bits off the bottom of the pan.
Add the lentils and sweet potato. Bring to a boil, then lower heat to simmer for about 20 minutes, until the lentils are cooked and the sweet potato is fork-tender.
Use an immersion blender to blend some of the soup in the pot, but make sure to leave a lot of texture. Add salt and pepper to taste, and stir in the lemon juice and kale. Simmer for another 5-10 minutes to allow the kale to soften.
Lastly, stir in the fresh cilantro or parsley. Serve in bowls with a scoop of cooked rice on top, some vegan naan or crusty bread. Enjoy!
