Step 1

Sauté the aromatics. In a large Dutch oven, heat about 2 tablespoons olive oil over medium-high heat. Add the onions, garlic, carrots, and celery. Season with a big pinch of salt and pepper. Cook, stirring occasionally until the veggies are fragrant and somewhat tender, about 5 minutes.

Step 2

Simmer. Add the tomatoes and lightly crush with a potato masher or the back of a fork. Stir in the vegetable broth, bay leaf, Italian seasoning, red pepper flakes, and lentils. Season with another pinch of kosher salt and black pepper. Bring the soup to a boil, then lower the heat and partly cover the Dutch oven, leaving a little opening. Simmer for about 20 to 30 minutes or until the lentils are very tender and cooked through, but still intact.

Step 3

Finish and serve. Turn off the heat and stir in the baby spinach, parsley, and a splash of red wine vinegar. Taste and season with more vinegar, salt, and pepper to your liking. Transfer to serving bowls and finish with a drizzle of olive oil and Parmesan cheese, if using.