Sauté the Aromatics: Heat the olive oil in a large ceramic or cast iron pot over medium heat. Add the finely diced onion and cook, stirring occasionally, until it turns golden and soft—this usually takes about 5 to 7 minutes. Then, add the minced garlic and stir for about 1 minute until fragrant.
Toast the Spices: Sprinkle in the coriander, cumin, sumac, crushed red pepper flakes, dried mint, and a pinch of sugar. Stir constantly for 2 minutes to allow the spices to release their aromatic oils, blending perfectly with the onions and garlic. Next, sprinkle the flour over the mixture and stir for another minute to create a light thickening base.
Add Liquids and Lentils: Pour in the vegetable broth and water, increasing the heat to high. Bring the mixture to a rolling boil. Once boiling, add the frozen spinach directly into the pot along with the rinsed lentils. Stir well to combine all ingredients.
Simmer to Perfection: Reduce the heat to medium-low, cover the pot, and let the soup simmer gently for 20 minutes, or until the lentils are tender. Check occasionally, and if the soup thickens too much, add a little hot water to maintain your preferred consistency.
Final Flavor Boost: Once the lentils have softened, remove the pot from heat. Stir in the fresh lime juice and chopped parsley for a bright, fresh finish. Cover the pot again and let the soup rest for 5 minutes to allow the flavors to meld.
Serve and Enjoy: Ladle the soup into bowls and serve hot, ideally paired with warm pita or rustic bread for a satisfying meal.