01 - Heat the olive oil in a large heavy-bottomed pot over medium heat. Add the chopped onion, diced carrots, and diced celery. Sauté, stirring occasionally, for about 5 minutes until the vegetables begin to soften and the onion turns translucent.
02 - Stir in the minced garlic, ground cumin, ground coriander, ground turmeric, and crushed red pepper flakes. Cook, stirring constantly, for about 1 minute until fragrant and the spices are well toasted.
03 - Add the rinsed lentils and pour in the vegetable broth. Bring the mixture to a rolling boil, then reduce the heat to low. Cover the pot and let it simmer gently for 25 to 30 minutes, or until the lentils are fully tender.
04 - Stir in the lemon zest, fresh lemon juice, and chopped parsley. Season generously with kosher salt and freshly ground black pepper to taste. Stir well to combine all the flavors.
05 - For a creamier, smoother consistency, use an immersion blender to partially purée the soup directly in the pot, leaving some texture intact. Skip this step if you prefer a fully rustic, chunky soup.
06 - Ladle the hot soup into individual bowls. Garnish with additional chopped parsley and an extra squeeze of lemon juice if desired. Drizzle with olive oil for added richness and serve immediately.