Heat in a large soup pot over medium-low heat:
Add and cook, stirring, until the vegetables are tender but not browned, 5 to 10 minutes:
- 1 large carrot, diced
- 1 celery rib, diced
- 1 large onion, diced
- 3 garlic cloves, minced
- (4 ounces pancetta or Canadian bacon, diced)
Stir in:
- 1 cup dried green or brown lentils, rinsed and picked over
- One 14 ½-ounce can diced tomatoes
- 1 teaspoon dried thyme
- 6 cups water
- ½ teaspoon salt
Bring to a boil, then reduce the heat, and simmer, covered, until the lentils are tender, 30 to 40 minutes. If desired, add for the last 5 minutes:
- (1 bunch kale, deribbed and thinly sliced)
Stir in:
- 1 ½ teaspoons lemon juice, sherry vinegar, or balsamic vinegar
- ½ teaspoon black pepper
- Salt to taste