Pour the oil into the port and place on the stove over medium heat.
Add the onion, sprinkle about 2 pinches of salt and cook, stirring occassionally, until onions soften and are translucent, about 5 minutes.
Add the carrots, celery, the rest of the salt and stir to combine. Continue to cook the rest of the veggies soften.
Add the lentils, broth or stock and bay leaf. Bring to a boil then reduce the heat to low and simmer covered until the lentils begin to fall apart, 20 to 30 minutes.
Then remove the soup from the burner and stir in the lemon juice.
Ladle the soup into bowls and top with your favorite topping, if desired.