As outside temperatures drop and winter begins to settle in, the warmth and comfort of soup is one of the best ways to stay toasty. Perhaps your favorite kind is a creamy tomato soup or classic chicken noodle, but if you’re a lentil soup fan, chef Ina Garten recommends one ingredient that will make your recipe sing.

Lentils, rich in protein, fiber, and minerals, have an earthy but somewhat one-note flavor, which can be lifted up using an acidic ingredient like lemon juice or vinegar. Garten adds a bit of red wine vinegar to her hearty lentil soup featuring leeks and tomato paste, saying, "I'm looking for some edge that kind of wakes everything up."

Garten says that her last-minute idea to add a splash of red wine vinegar to the soup was exactly the finishing touch she needed. Fellow celebrity chef Martha Stewart recommends the same ingredient for her own lentil soup, since most hearty slow-simmered dishes benefit from a bit of acid on top for the most complex flavor.