Heat the oil in a large stock pot over medium heat then add the onion, celery and carrots. Cook, stirring frequently until the vegetables are soft and the onions are translucent, about 3-4 minutes. Add the minced garlic and cook for another minute, until fragrant.
1-2 tablespoons olive oil or avocado oil, 1 medium yellow onion, 3 large carrots, 2 stalks celery, 4 cloves garlic
Pour the vegetable stock over the vegetables, then add the red lentils, bay leaves, turmeric and cumin and stir well. Turn the heat up to medium-high to bring the soup to a boil then reduce the heat to medium-low to simmer. Cover and simmer for 12-15 minutes, until the lentils are very tender and beginning to break down.
6 cups vegetable stock, 1 1/2 cups red lentils, 2 bay leaves, 1/2 teaspoon turmeric, 1 teaspoon cumin
Remove the lid and stir in the lemon juice, lemon zest, salt and pepper.
1/2 teaspoon black pepper, 1 teaspoon kosher salt, Juice from 1 lemon (about 5 tbsps), 1 teaspoon lemon zest
Transfer 2 cups of soup to a blender and blend on high until smooth, then pour it back into the soup and stir to combine. This gives the soup a creamy consistency while still leaving plenty of texture. You can also use an immersion blender to partially blend the soup to your desired consistency.
Add the spinach or kale, if using, and cook for 2-3 minutes, until wilted. Taste and add more salt, pepper, or lemon juice as needed. Serve with freshly cracked black pepper and cilantro or parsley.