Heat the avocado oil (or olive oil) in a large nonstick skillet over medium-high heat. Add the onion and sauté, stirring frequently, until the onion begins to brown, about 8 to 10 minutes. For the best flavor, you want the onion to nearly be caramelized. Add the garlic and cook for another 2 to 3 minutes, until the garlic is fragrant. Transfer the sauteed onion and garlic to the slow cooker.
Transfer the rest of the ingredients for the lentil soup to the crock pot and stir well.
Secure the lid on the slow cooker and slow cook on High for 3 to 4 hours or Low for 6 to 8 hours.
Once the lentil soup has finished cooking, give it a big stir, discard the bay leaf, and taste the soup for flavor. Add sea salt and/or lemon juice to taste.
Serve lentil soup in big bowls with crusty bread or cornbread.
Notes
For creamy lentil soup, use an immersion blender to blend the soup until it reaches your desired texture.If you prefer soups with a lot of liquid, increase the amount of broth to 6-8 cups total, depending on how much broth you enjoy in soup.This soup is more flavorful the longer it sits and tastes even better the next day. If you can make it one day in advance to allow the flavors to develop, it is well worth the patience!Store any leftover lentil soup in an airtight container in the refrigerator for up to 5 days. If you’d like to freeze this soup, double bag two large 1-gallon freezer bags and secure them tightly. Freeze for up to three months.