Bloom the spices - Heat the olive oil in a large pot over medium heat. Add the garam masala, cumin, turmeric, paprika, cinnamon, coriander, ground ginger, and cayenne, if using. Stir for about 30 seconds to toast the spices and release their aroma.
1 tbsp + 1 teaspoon garam masala, 1 tbsp cumin, 1 tsp turmeric, 1 tsp paprika, ½ tsp ground cinnamon, 1 tsp coriander, ½ tsp ginger powder, ½ tsp cayenne, ⅓ cup olive oil
Sauté the aromatics - Add the diced onion and carrot if using, and cook until softened and the onion is translucent, about 5-8 minutes. Add the fresh ginger and minced garlic and cook for another 3 minutes, until fragrant. If you notice the pan drying out, feel free to add a drizzle more olive oil, or a splash of water.
1 yellow onion, 1 carrot, 1 tsp grated fresh ginger, 5 cloves garlic
Add the lentils and vegetables - Pour in the chicken or vegetable stock and add the rinsed lentils, diced sweet potatoes, and tomatoes. Season with kosher salt and stir to combine. Add 2 cups of water and stir.
1 ½ cups dry, uncooked lentils, 4 cups stock or broth, 2 cups filtered water, 1 tbsp kosher salt, 2 medium-large sweet potatoes, 28 oz canned diced tomatoes
Simmer the soup - Bring the soup to a boil, then reduce the heat and simmer until the lentils and sweet potatoes are tender. Stir occasionally as the soup cooks. If foamy bubbles appear on the top of the soup, remove using a spoon and discard.
Blend until creamy - Use an immersion blender to partially blend the soup, leaving some of the lentils and vegetables intact for texture. Alternatively you can transfer a portion of the soup to a regular blender or food processor and blend until smooth before returning it to the pot. Blend more for a creamier soup, and blend less for a chunkier result.
Add the spinach - Stir in the baby spinach. The residual heat of the soup will cook the spinach after about 5 minutes.
4 oz fresh spinach
Finish with lemon juice and serve - Stir in the fresh lemon juice and taste the soup, adding more kosher salt or lemon juice as needed to balance the flavors. Ladle the soup into bowls and serve warm with your favorite toppings or alongside warm naan or rice.
½ lemon