Heat the olive oil in a large Dutch oven or pot over medium heat. One-fourth cup olive oil may seem excessive, but it gives a delightful richness and heartiness to this healthful soup.
When the oil is shimmering, add the chopped onion and carrot and cook, stirring frequently, until the onion softens and turns translucent, about 5 minutes.
Combine the garlic, cumin, curry powder, and thyme. Cook for about 30 seconds or until aromatic, stirring regularly. Pour in the drained diced tomatoes and simmer for a few more minutes, stirring frequently, to intensify the taste.
Pour in the lentils, broth, and water. Combine 1 teaspoon salt and a pinch of red pepper flakes. Season generously with fresh ground black pepper. Bring the mixture to a boil, then partially cover and decrease heat to a slow simmer. Cook for 25–30 minutes, or until the lentils are cooked but still maintain their shape.
Add 2 cups of the soup to a blender. Secure the lid, cover it with a tea towel to protect your hand from steam, and purée the soup until smooth. Pour the pureed soup back into the pot. (Alternatively, use an immersion blender to mix a part of the soup.
Cook for an additional 5 minutes, or until the greens are tender enough to your preference. Remove the pot from the heat and add 1 tablespoon lemon juice. Taste and season with extra salt, pepper, and/or lemon juice until the flavors are bursting. For a hotter soup, add an extra pinch or two of red pepper flakes.
Serve while heated. Leftovers can be stored in the refrigerator for up to four days or frozen for several months.