Heat olive oil in a large pot over medium heat. Add the chopped onion and sauté until translucent, about 5 minutes.
Stir in the minced garlic, diced carrot, and celery. Cook for another 3-4 minutes until the vegetables start to soften.
Add the ground cumin, turmeric, and smoked paprika to the pot, stirring for about 1 minute until fragrant.
Add the rinsed red lentils, vegetable broth, and diced tomatoes (with their juice). Bring to a boil, then reduce the heat to a simmer.
Cover and cook for approximately 25-30 minutes, or until the lentils are tender. Stir occasionally and add more broth or water if the soup becomes too thick.
Once the lentils are cooked, stir in the chopped kale and cook for an additional 5 minutes until the kale is wilted.
Season the soup with salt, pepper, and lemon juice. Adjust seasoning to your taste.
Remove from heat and let cool slightly before serving.
Notes
Serve warm garnished with fresh cilantro and lemon for added freshness.