For a richer flavor, consider adding a teaspoon of smoked paprika or a pinch of red pepper flakes to the soup. If you don't have a pressure cooker, you can simmer the soup on the stovetop for approximately 45 minutes to 1 hour, or until the lentils are tender. Feel free to experiment with other vegetables, such as carrots, celery, or spinach, to customize the soup to your liking. The soup can be stored in the refrigerator for up to 3 days.