In a large pot, heat the olive oil over medium heat. Add the onion and saute for 5 to 6 minutes, until the onion is translucent. Add the garlic and cook for 30 seconds. Add the celery and lightly season with salt. Saute for 2 to 3 minutes.
Add the bay leaf, cumin, chili powder, coriander, paprika and cayenne pepper. Stir to combine. Saute for a couple of minutes and until fragrant.
Add the tomatoes with juices, broth and lentils. Bring the mixture to a boil, then reduce the heat to medium and simmer (uncovered) for 20 to 25 minutes. The lentils should be tender. Remove the bay leaf.
Stir in the kale and cook for few minutes until the kale is tender and wilted. Season with salt and pepper.