Heat coconut oil in a heavy soup pot and sauté onions, carrot, celery and garlic for 5 to 8 minutes or until onion is transparent.
Mix coriander, cumin, turmeric, paprika, cinnamon, salt and pepper in a small bowel and then add to the pot. Continue to cook for 2 to 3 minutes, until fragrant.
Add the cubed sweet potato and rinsed/drained lentils and stir to combine with the sautéed vegetables.
Add the bay leaf and vegetable stock and bring to a boil. Reduce heat, cover and simmer for 20 minutes or until the sweet potato is cooked. While the soup is simmering, chop the kale into bite sized pieces and juice the lemon.
Remove the bay leaf and use an immersion blender to partially purée soup to yield a creamy, yet rustic texture (about 1/2 of the soup). Alternatively, transfer one third of the soup to a blender, blend and return to pot for mixing. If you are not using a vented blender such as a Vitamix, you will need to let the soup cool first so that it doesn't explode in the blender!
Add the kale and lemon juice. Heat for about another 5 minutes. Kale should be wilted. Ladle into bowls and enjoy!