In a large pot, heat the olive oil over medium heat. Add diced onions and celery and sauté until softened, about 3 minutes.
1 large white onion, 1 tablespoons olive oil
Add garlic, diced carrot, and sweet potato. Continue cooking for about 3 more minutes, allowing the vegetables to soften. Stir often to prevent browning the vegetables.
1 medium carrot, 1 celery stalk, 1 sweet potato, 3 cloves garlic
Stir in cumin, ground coriander, turmeric, smoked paprika, and cinnamon. Cook for another minute until the spices are fragrant.
1 teaspoon ground cumin, 1 teaspoon ground coriander, 1 teaspoon turmeric, ½ teaspoon smoked paprika, ¼ teaspoon cinnamon
Add lentils, harissa paste, and salt into the pot. Mix well to coat everything in the spices.
1 tablespoon harissa paste, 1 cup brown lentils, 1 cup red lentils, 2 teaspoons salt
Pour in the vegetable or chicken broth. Bring to a boil, then reduce the heat to simmer. Cover and let cook for 25-30 minutes or until lentils and vegetables are tender.
6 cups vegetable or chicken broth
Remove from heat and stir in freshly squeezed lemon juice and fresh coriander or parsley. Adjust seasonings if needed.
½ lemon, ½ cup fresh coriander or parsley
Ladle the soup into bowls and garnish with fresh extra coriander or parsley.