Place a large saucepan over medium heat and add the oil. Add the onion and garlic and cook, stirring often, until the onion is softened, about 5 minutes.
Add the lentils and vegetable broth and bring to a boil. Lower the heat and cover the pot, allowing the mixture to simmer gently until the lentils are tender, about 45 minutes.
Stir in the chard, salt and pepper, and cook, stirring occasionally, until the chard is wilted, about 5 minutes.
Stir in the vinegar.
Taste and adjust the seasonings, adding more salt, pepper and/or vinegar as necessary.
Notes
Serving size: 1-1/2 cupsWW Points: 1Check the WW Points for this recipe and track it in the WW app. (Must be logged into WW on a smartphone or tablet.)5PointsPlus (Old plan)I added about 1 cup of leftover cooked polenta to this soup so it wouldn't go to waste, which thickened it up quite a bit.You could also and 1-2 cups of diced tomatoes along with the lentils and broth, for more color and flavor if you wanted.Be sure to pick over your lentils and remove any stones. Every time I'm tempted to skip this step, I think back to a cooking class I took where the instructor explained she once found a small piece of metal in the lentils she was preparing for a catering event!