Peel the vegetables and cut them into small pieces.

Place the vegetables and butter in a pot over heat and sauté briefly.

Add the washed lentils, salt, cumin, and 6 cups water (about 1.4 liters) to the pot. Bring to a boil.

Reduce to medium heat and cook for about 20 minutes, or until the vegetables are tender.

Remove the soup from heat and puree until smooth.

Serve hot, topped with parsley, toasted bread, and a squeeze of lemon juice.