Step 1

Heat oil in a Dutch oven or large pot over medium heat. Add onion, carrot and celery mix; cook, stirring occasionally, until softened, 6 to 10 minutes. Add garlic; cook, stirring often, until fragrant, about 30 seconds.

Step 2

Stir in broth, lentils, tomatoes, thyme, salt, pepper, crushed red pepper and Parmesan rind, if using. Bring to a boil over medium-high heat. Reduce heat to medium-low; cover and cook, stirring occasionally, until the lentils are almost tender, 15 to 25 minutes, adding water as needed to thin to desired consistency.

Step 3

Stir in kale. Cook, covered, until the kale is tender, 5 to 10 minutes. Remove and discard the Parmesan rind, if using. Stir in vinegar. Divide the soup among 6 bowls; sprinkle with Parmesan. Garnish with parsley, if desired.