This is our goto lentil soup recipe and honestly, it never disappoints. We use dried lentils because they taste better than canned ones. Dried lentils are also easier to store and keep for a very long time. Lentils do not require soaking like other pulses.
In a large pot, heat the olive oil over moderate heat. Add the onion & carrots and sauté for 5 minutes. One-fourth cup olive oil may seem like a lot, but it adds a really nice richness to the soup.
Add the garlic, cumin, curry powder, and thyme and cook for 1 minute until fragrant.
Pour in the drained diced tomatoes and cook for a few more minutes, stirring often, in order to enhance their flavor.
Pour in the lentils, broth, and water. Add 1 teaspoon salt and a pinch of red pepper flakes. Season generously with freshly ground black pepper.
Raise heat and bring the mixture to a boil, then partially cover the pot and reduce the heat to maintain a gentle simmer. Cook for 25 to 30 minutes until the lentils are tender.
Transfer 1/2 of the soup to a blender (or use an immersion blender) and puree until smooth.
Add the chopped kale (or other greens) and cook for 5 more minutes until the greens have softened. Remove the pot from the heat and stir in 1 tablespoon of lemon juice.
Taste and season with more salt, pepper, and/or lemon juice.