For this lentil recipe, I decided to keep it simple so the heady flavor of the beans could really shine. Resist the urge to clutter the flavor with too many herbs or spices, which would make it a totally different kind of soup. Here, you need only a Parmesan rind, that nubby end of cheese that most people throw away. Next time you spend good money for real Parmeggiano-Reggiano, keep the rind and store it in the freezer for later use.
In a large Dutch oven, heat olive oil and sautée the onion and ½ teaspoon of salt over medium heat until it starts to lose its raw smell. Add the carrots and celery and cook, stirring occasionally, until all the vegetables start to take on a golden color, about 10 minutes. As the vegetables start to lose water, their song will be a mellow hum, rather than the hiss they make when you first put them in. That’s the moment to add the garlic and give a good stir. All of a sudden, the garlic will reach up and charm you into its sensual embrace and you’ll feel like you just want to run off with the garlic then and there, but focus here. You need to finish raising these beans and water into a fabulous soup. It’ll be worth it.
Add the lentils and stir around until they look slick with olive oil. Add the can of tomatoes, juices and all, water, Parmesan rind, bay leaf and the remainder of salt. Bring to a brisk boil and then immediately turn it down to simmer. Cook on low for about a half hour. When it’s done, turn the heat off and let the soup sit on the stovetop for about an hour before reheating to serve. Alternately, you could refrigerate for up to a week and serve at a later time. When you reheat, check the seasonings and adjust the seasonings with salt and pepper and a drop or two of red wine vinegar.
Note: Don’t skip this resting phase of making the soup. It really will have more depth and taste creamier after the flavors have lived together for a while. A lot of cooks have discovered this anecdotally, but I swear I read a scientific explanation for it, but for the life of me, I just can’t find it anywhere. If you happen to have an article where Cook’s Illustrated explains why soups and stews taste better the next day, will you send it my way?