Step 1: Sauté the Aromatics : In a large soup pot, heat olive oil over medium heat. Add the onion and cook until translucent, about 4 minutes. Stir in garlic, carrots, and celery, cooking another 2–3 minutes until softened.
Step 2: Toast the Spices : Add all the spices (cumin, coriander, paprika, cinnamon, turmeric, ginger, cayenne). Stir for about 30 seconds to release their aroma — this step “blooms” the spices, deepening their flavor.
Step 3: Add Lentils and Tomatoes : Stir in the rinsed lentils, tomato paste, and diced tomatoes. Mix well to coat everything with the spices.
Step 4: Simmer the Soup : Pour in vegetable broth and water. Bring to a boil, then reduce the heat to low. Cover partially and simmer for 25–30 minutes, stirring occasionally, until lentils are soft and the soup thickens.
Step 5: Blend (Optional) : For a creamier texture, use an immersion blender to blend half the soup — leave some lentils whole for texture. Alternatively, transfer half to a blender, blend until smooth, and pour back in.
Step 6: Season and Serve : Taste and adjust seasoning with salt and pepper. Serve hot, garnished with fresh cilantro or parsley, a drizzle of olive oil, and a squeeze of lemon juice.