1. Peel and dice the onion, carrots, and sweet potato. Dice the celery. Peel and slice the garlic. Chop the kale
2. Heat the canola oil in a large stockpot or Dutch oven over medium-low heat. Add the onion, carrots, celery, and garlic and season with 1 teaspoon of the kosher salt. Sweat the vegetables (cook over low heat, stirring frequently) until they begin to soften, about 8 minutes, taking care that they don’t brown.
3. Add the tomato paste, stir, and cook for 2 to 3 minutes. Add the lentils and stock and turn up the heat to high to bring to a boil, then turn down the heat to maintain a low simmer and cook for 15 minutes. Add the sweet potato and continue to cook until the lentils are softened and tender, 20 to 25 minutes more.
4. Add the kale and stir, cooking until it has just begun to wilt into the soup, 3 to 4 minutes. Season with the cayenne, the remaining 1 teaspoon salt, and the black pepper. Stir again and serve hot!