Heat the olive oil in a large pot over medium-high heat. Add the onion, carrots, and celery and saute for 5 minutes or so until softened, but not brown. Stir in the garlic and spices, and season with salt and pepper. Let cook for 1 minute or so until the garlic is fragrant (but not brown).
Add the lentils, tomatoes (and juices), and vegetable stock and bring the mixture to a boil, stirring occasionally. Reduce the heat to a simmer and let cook for 20 to 30 minutes or until thickened; remove from heat. If you like, you can use a stick blender to puree the soup to your desired consistency. Or feel free to leave it as is.
Stir in the kale and cook over low heat for a minute or two until wilted. Taste, and season generously with salt and pepper. Serve in shallow bowls with crusty bread.