1 1/2cupsFrench green lentilsor brown lentils; I do not recommend red lentils, which are more delicate and break down when cooked for a long period
1can fire-roasted diced tomatoes15 ounces
1can crushed tomatoes15 ounces
4cupslow-sodium vegetable broth
Parmesan rindoptional; add it if you have it
1tablespoonred wine vinegar
For serving: chopped fresh parsley and Parmesan
In a large skillet, heat the olive oil over medium high. Once the oil is hot, add the onion. Cook the onion, stirring often, until it is very soft and beginning to nicely brown and break down, about 8 minutes. Add the carrots, celery, Italian seasoning, salt, smoked paprika, and pepper. Sauté until the carrots and celery are barely soft, about 2 minutes. Add the garlic and cook just until fragrant, about 30 seconds. Transfer to a 6-quart or larger slow cooker.
To the slow cooker, add the lentils, diced tomatoes, crushed tomatoes, and vegetable broth. Cover and cook on high for 3 to 4 hours or low for 6 to 8 hours, or until the lentils are tender and retain a slight amount of pleasant chew but are not mushy.
Remove the Parmesan rind (if using). Stir in the red wine vinegar and sugar. If the soup is too thick for your liking, thin with a bit of water or additional broth until you reach your desired consistency. Taste and adjust the seasonings as desired. Serve hot with a sprinkle of parsley, Parmesan (if using), and bread for dipping.
TO STORE: Store leftovers in an airtight container in the refrigerator for up to 5 days.
TO REHEAT: Reheat gently in the microwave or on the stovetop with a little water or additional broth to thin as needed.
TO FREEZE: Place soup in an airtight freezer-safe storage container in the freezer for up to 3 months. Let thaw overnight in the refrigerator before reheating.
TO MAKE ON THE STOVETOP: Prepare the recipe in a large Dutch oven on the stove through Step 3. Bring the soup to a boil, cover, and reduce the heat to a simmer. Let cook until the lentil are tender but not mushy, about 25 minutes, stirring once or twice throughout. Enjoy hot.