Start by heating the olive oil in a large pot over medium heat until it shimmers.
Add the onion and carrots to the pot, cooking until the onion is soft and translucent, about 5 minutes.
Stir in the garlic, cumin, curry powder, and thyme, cooking until fragrant, roughly 30 seconds.
Mix in the diced tomatoes and let them simmer for a few minutes to deepen their flavor.
Add the lentils, vegetable broth, water, salt, red pepper flakes, and black pepper. Bring to a boil, then simmer gently, partially covered, until lentils are tender, about 25 to 30 minutes.
Blend 2 cups of the soup until smooth, then return it to the pot to thicken the soup.
Stir in the chopped greens and cook until they're soft. Finish by adding lemon juice and adjusting the seasoning to your taste.
Serve the soup hot. Store leftovers in the fridge for up to 4 days or freeze for longer storage.