Build the Aromatic Base: In a large Dutch oven or heavy-bottomed pot, warm the extra virgin olive oil over medium heat. Add the chopped onion and sliced leek, stirring occasionally for 6-8 minutes, until they are very soft and translucent. Add the minced garlic and cook for another minute until fragrant.
Infuse the Root Vegetables: Add the diced carrots and parsnip to the pot. Sauté for 5 minutes, allowing the vegetables to soften slightly and release their natural sweetness.
Bloom the Spices: Stir in the tomato paste, cumin, smoked paprika, coriander, and cayenne pepper. Cook for 2 minutes, stirring constantly. This step toasts the spices and deepens the tomato flavor, creating a rich, savory base.
Simmer the Soup: Pour the rinsed lentils, low-sodium vegetable broth, and water into the pot. Stir everything to combine, increase the heat to high, and bring the mixture to a boil.
Cook to Perfection: Once boiling, reduce the heat to low, cover the pot, and let the soup simmer gently for 20-25 minutes, or until the lentils are completely soft and falling apart.
Create the Velvety Texture: Turn off the heat. Use an immersion blender to carefully puree the soup directly in the pot until it reaches your desired consistency—from partially textured to completely smooth and creamy. If using a standard blender, allow the soup to cool slightly before blending in batches.
Finish and Serve: Stir in the fresh lemon zest and juice. Divide the soup among six bowls, garnish with a final drizzle of extra virgin olive oil, fresh parsley, and a pinch of Aleppo pepper, if desired.