I like to prepare this red lentil soup in my slow cooker the night before and start it in the morning before work! Then all I have to do when I come home is add some kale and lemon juice - soooo easy.
Combine all of the soup ingredients in a large slow cooker. Cook on high 4-6 hours or on low for 8-10 hours, until the vegetables and lentils are tender.
Optional: Using an immersion (or regular) blender, puree about half of the soup. (Note: If using a regular blender, don't fill it too much, or you will have a soup explosion on your hands!). Add it back to the pot and stir well. *This step is not necessary*. I just like the texture, but it's good either way!
Stir the kale and lemon juice into the soup. Cook for about 15 minutes, or until the kale is wilted but not soggy. Serve with a drizzle of cream or yogurt (coconut works great to keep it vegan!), lemons, cilantro, and crusty bread.